diff --git a/core/app.py b/core/app.py
index 887572cb..1de58221 100644
--- a/core/app.py
+++ b/core/app.py
@@ -353,6 +353,11 @@ class DupeGuru(RegistrableApplication, Broadcaster):
             logging.warning("dupeGuru Warning: %s" % str(e))
         return False
     
+    def reprioritize_groups(self, sort_key):
+        for group in self.results.groups:
+            group.prioritize(key_func=sort_key)
+        self._results_changed()
+    
     def reveal_selected(self):
         if self.selected_dupes:
             self._reveal_path(self.selected_dupes[0].path)
diff --git a/core/gui/prioritize_dialog.py b/core/gui/prioritize_dialog.py
index 63287c81..e4704e83 100644
--- a/core/gui/prioritize_dialog.py
+++ b/core/gui/prioritize_dialog.py
@@ -21,10 +21,30 @@ class CriterionCategoryList(SelectableList):
 
 class PrioritizeDialog:
     def __init__(self, view, app):
+        self.app = app
         self.categories = [KindCategory(app.results)]
         self.category_list = CriterionCategoryList(self)
-        self.criteria_list = []
+        self.criteria = []
+        self.criteria_list = SelectableList()
+        self.prioritizations = []
     
+    #--- Private
+    def _sort_key(self, dupe):
+        # Our sort key consists of a tuple of inverted bool values represented as ints. When a dupe
+        # fits a criteria, we want it at the top of the listm and thus we'll give it the value 0.
+        # When the dupe doesn't fit a criteria, we ant it at the bottom, and we give the value 1.
+        result = (crit.test_dupe(dupe) for crit in self.prioritizations)
+        return tuple((0 if value else 1) for value in result)
+    
+    #--- Public
     def select_category(self, category):
-        criteria = category.criteria_list()
-        self.criteria_list = [c.value for c in criteria]
+        self.criteria = category.criteria_list()
+        self.criteria_list[:] = [c.value for c in self.criteria]
+
+    def add_selected(self):
+        # Add selected criteria in criteria_list to prioritization_list.
+        crit = self.criteria[self.criteria_list.selected_index]
+        self.prioritizations.append(crit)
+    
+    def perform_reprioritization(self):
+        self.app.reprioritize_groups(self._sort_key)
diff --git a/core/prioritize.py b/core/prioritize.py
index a95b3898..0f973121 100644
--- a/core/prioritize.py
+++ b/core/prioritize.py
@@ -29,6 +29,9 @@ class Criterion:
         self.category = category
         self.value = value
     
+    def test_dupe(self, dupe):
+        return self.category._extract_value(dupe) == self.value
+    
     @property
     def display(self):
         return "{} ({})".format(self.category, self.value)
diff --git a/core/tests/prioritize_test.py b/core/tests/prioritize_test.py
index 41d4dc01..a0e8f39d 100644
--- a/core/tests/prioritize_test.py
+++ b/core/tests/prioritize_test.py
@@ -40,4 +40,14 @@ def app_normal_results():
 def test_kind_subcrit(app):
     # The subcriteria of the "Kind" criteria is a list of extensions contained in the dupes.
     app.select_pri_criterion("Kind")
-    eq_(app.pdialog.criteria_list, ['ext1', 'ext2'])
\ No newline at end of file
+    eq_(app.pdialog.criteria_list[:], ['ext1', 'ext2'])
+
+@with_app(app_normal_results)
+def test_perform_reprioritization(app):
+    # Just a simple test of the system as a whole.
+    # select a criterion, and perform re-prioritization and see if it worked.
+    app.select_pri_criterion("Kind")
+    app.pdialog.criteria_list.select([1]) # ext2
+    app.pdialog.add_selected()
+    app.pdialog.perform_reprioritization()
+    eq_(app.rtable[0].data[0], 'foo2.ext2')