diff --git a/umap/forms.py b/umap/forms.py
index d90d7068..15f39514 100644
--- a/umap/forms.py
+++ b/umap/forms.py
@@ -113,11 +113,25 @@ class UserProfileForm(forms.ModelForm):
         fields = ("username", "first_name", "last_name")
 
 
+class GroupMembersField(forms.ModelMultipleChoiceField):
+    def set_choices(self, choices):
+        iterator = self.iterator(self)
+        # Override queryset so to expose only selected choices:
+        # - we don't want a select with 100000 options
+        # - the select values will be used by the autocomplete widget to display
+        #   already existing members of the group
+        iterator.queryset = choices
+        self.choices = iterator
+
+
 class GroupForm(forms.ModelForm):
     class Meta:
         model = Group
         fields = ["name", "members"]
 
-    members = forms.ModelMultipleChoiceField(
-        queryset=User.objects.all(), widget=forms.CheckboxSelectMultiple
-    )
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.fields["members"].set_choices(self.initial["members"])
+        self.fields["members"].widget.attrs["hidden"] = "hidden"
+
+    members = GroupMembersField(queryset=User.objects.all())
diff --git a/umap/static/umap/content.css b/umap/static/umap/content.css
index 04cc8946..6a9fe92e 100644
--- a/umap/static/umap/content.css
+++ b/umap/static/umap/content.css
@@ -273,9 +273,7 @@ ul.umap-autocomplete {
     border: 1px solid #202425;
     padding: 7px;
     color: #eeeeec;
-}
-.umap-multiresult li + li {
-    margin-top: 7px;
+    margin-bottom: 7px;
 }
 .umap-singleresult div .close,
 .umap-multiresult li .close {
diff --git a/umap/static/umap/js/modules/autocomplete.js b/umap/static/umap/js/modules/autocomplete.js
index e693d6be..1eadd791 100644
--- a/umap/static/umap/js/modules/autocomplete.js
+++ b/umap/static/umap/js/modules/autocomplete.js
@@ -9,8 +9,8 @@ import { Request, ServerRequest } from './request.js'
 import { escapeHTML, generateId } from './utils.js'
 
 export class BaseAutocomplete {
-  constructor(el, options) {
-    this.el = el
+  constructor(parent, options) {
+    this.parent = parent
     this.options = {
       placeholder: translate('Start typing...'),
       emptyMessage: translate('No result'),
@@ -43,7 +43,7 @@ export class BaseAutocomplete {
     this.input = DomUtil.element({
       tagName: 'input',
       type: 'text',
-      parent: this.el,
+      parent: this.parent,
       placeholder: this.options.placeholder,
       autocomplete: 'off',
       className: this.options.className,
diff --git a/umap/templates/auth/group_form.html b/umap/templates/auth/group_form.html
index 16ea81e6..45af6d13 100644
--- a/umap/templates/auth/group_form.html
+++ b/umap/templates/auth/group_form.html
@@ -25,4 +25,34 @@
       {% endif %}
     </div>
   </div>
+  <script type="module" defer>
+    const form = document.querySelector("#group_form")
+    const select = form.querySelector('#id_members')
+    function onSelect({item: {value, label}}) {
+      const option = document.createElement('option')
+      option.value = value
+      option.textContent = label
+      option.selected = "selected"
+      select.appendChild(option)
+    }
+    function onUnselect({item: {value, label}}) {
+      const option = select.querySelector(`[value="${value}"]`)
+      select.removeChild(option)
+    }
+    const options = {
+      className: 'edit-group-members',
+      on_select: onSelect,
+      on_unselect: onUnselect,
+      placeholder: "{% trans "Add user" %}"
+    }
+    const autocomplete = new U.AjaxAutocompleteMultiple(form, options)
+    for (const option of select.options) {
+      autocomplete.displaySelected({
+        item: { value: option.value, label: option.textContent },
+      })
+    }
+    const submit = form.querySelector('input[type="submit"]')
+    // Move it after the autocomplete widget.
+    form.appendChild(submit)
+  </script>
 {% endblock maincontent %}
diff --git a/umap/tests/integration/test_group.py b/umap/tests/integration/test_group.py
new file mode 100644
index 00000000..bd9a4746
--- /dev/null
+++ b/umap/tests/integration/test_group.py
@@ -0,0 +1,46 @@
+import re
+
+import pytest
+from django.contrib.auth.models import Group
+
+pytestmark = pytest.mark.django_db
+
+
+def test_can_add_user_to_group(live_server, map, user, group, login):
+    map.owner.groups.add(group)
+    map.owner.save()
+    assert Group.objects.count() == 1
+    page = login(map.owner)
+    with page.expect_navigation():
+        page.get_by_role("link", name="My teams").click()
+    with page.expect_navigation():
+        page.get_by_role("link", name="Edit").click()
+    page.get_by_placeholder("Add user").click()
+    with page.expect_response(re.compile(r".*/agnocomplete/.*")):
+        page.get_by_placeholder("Add user").press_sequentially("joe")
+    page.get_by_text("Joe").click()
+    page.get_by_role("button", name="Save").click()
+    assert Group.objects.count() == 1
+    modified = Group.objects.first()
+    assert user in modified.user_set.all()
+
+
+def test_can_remove_user_from_group(live_server, map, user, user2, group, login):
+    map.owner.groups.add(group)
+    map.owner.save()
+    user.groups.add(group)
+    user.save()
+    user2.groups.add(group)
+    user2.save()
+    assert Group.objects.count() == 1
+    page = login(map.owner)
+    with page.expect_navigation():
+        page.get_by_role("link", name="My teams").click()
+    with page.expect_navigation():
+        page.get_by_role("link", name="Edit").click()
+    page.locator("li").filter(has_text="Averell").locator(".close").click()
+    page.get_by_role("button", name="Save").click()
+    assert Group.objects.count() == 1
+    modified = Group.objects.first()
+    assert user in modified.user_set.all()
+    assert user2 not in modified.user_set.all()
diff --git a/umap/tests/test_group_views.py b/umap/tests/test_group_views.py
index d880f850..0135c1bd 100644
--- a/umap/tests/test_group_views.py
+++ b/umap/tests/test_group_views.py
@@ -37,7 +37,7 @@ def test_can_create_a_group(client, user):
     assert group in user.groups.all()
 
 
-def test_can_edit_a_group(client, user, group):
+def test_can_edit_a_group_name(client, user, group):
     user.groups.add(group)
     user.save()
     assert Group.objects.count() == 1
@@ -52,6 +52,38 @@ def test_can_edit_a_group(client, user, group):
     assert modified in user.groups.all()
 
 
+def test_can_add_user_to_group(client, user, user2, group):
+    user.groups.add(group)
+    user.save()
+    assert Group.objects.count() == 1
+    url = reverse("group_update", args=(group.pk,))
+    client.login(username=user.username, password="123123")
+    response = client.post(url, {"name": group.name, "members": [user.pk, user2.pk]})
+    assert response.status_code == 302
+    assert response["Location"] == "/en/me/groups"
+    assert Group.objects.count() == 1
+    modified = Group.objects.first()
+    assert user in modified.user_set.all()
+    assert user2 in modified.user_set.all()
+
+
+def test_can_remove_user_from_group(client, user, user2, group):
+    user.groups.add(group)
+    user.save()
+    user2.groups.add(group)
+    user2.save()
+    assert Group.objects.count() == 1
+    url = reverse("group_update", args=(group.pk,))
+    client.login(username=user.username, password="123123")
+    response = client.post(url, {"name": group.name, "members": [user.pk]})
+    assert response.status_code == 302
+    assert response["Location"] == "/en/me/groups"
+    assert Group.objects.count() == 1
+    modified = Group.objects.first()
+    assert user in modified.user_set.all()
+    assert user2 not in modified.user_set.all()
+
+
 def test_cannot_edit_a_group_if_not_member(client, user, user2, group):
     user.groups.add(group)
     user.save()
diff --git a/umap/urls.py b/umap/urls.py
index 0f466ae4..ca75a7ab 100644
--- a/umap/urls.py
+++ b/umap/urls.py
@@ -25,6 +25,10 @@ admin.autodiscover()
 urlpatterns = [
     re_path(r"^admin/", admin.site.urls),
     re_path("", include("social_django.urls", namespace="social")),
+    re_path(
+        r"^agnocomplete/",
+        include(("agnocomplete.urls", "agnocomplete"), namespace="agnocomplete"),
+    ),
     re_path(r"^m/(?P<pk>\d+)/$", views.MapShortUrl.as_view(), name="map_short_url"),
     re_path(r"^ajax-proxy/$", cache_page(180)(views.ajax_proxy), name="ajax-proxy"),
     re_path(
@@ -40,7 +44,6 @@ urlpatterns = [
         name="password_change_done",
     ),
     re_path(r"^i18n/", include("django.conf.urls.i18n")),
-    re_path(r"^agnocomplete/", include("agnocomplete.urls")),
     re_path(r"^map/oembed/", views.MapOEmbed.as_view(), name="map_oembed"),
     re_path(
         r"^map/(?P<map_id>\d+)/download/",
diff --git a/umap/views.py b/umap/views.py
index 12282317..6eebf52e 100644
--- a/umap/views.py
+++ b/umap/views.py
@@ -213,9 +213,16 @@ class GroupUpdate(UpdateView):
         return initial
 
     def form_valid(self, form):
-        for user in form.cleaned_data["members"]:
-            user.groups.add(self.object)
-            user.save()
+        actual = self.object.user_set.all()
+        wanted = form.cleaned_data["members"]
+        for user in wanted:
+            if user not in actual:
+                user.groups.add(self.object)
+                user.save()
+        for user in actual:
+            if user not in wanted:
+                user.groups.remove(self.object)
+                user.save()
         return super().form_valid(form)