diff --git a/pgd/pgd_core/models.py b/pgd/pgd_core/models.py
index 5da558e..50bbd29 100644
--- a/pgd/pgd_core/models.py
+++ b/pgd/pgd_core/models.py
@@ -8,7 +8,7 @@ class Protein(models.Model):
     code        = models.CharField(max_length=4, primary_key=True, unique=True)
     threshold   = models.IntegerField() # new type; this should probably be a boolean type
     resolution  = models.FloatField(db_index=True)
-    rfactor     = models.FloatField()
+    rfactor     = models.FloatField(db_index=True)
     
     def __unicode__(self):
         return self.code
diff --git a/pgd/pgd_search/models.py b/pgd/pgd_search/models.py
index 871af91..e84cb29 100644
--- a/pgd/pgd_search/models.py
+++ b/pgd/pgd_search/models.py
@@ -33,6 +33,8 @@ class Search(models.Model):
     threshold        = models.IntegerField(null=True)
     resolution_min   = models.FloatField(null=True)
     resolution_max   = models.FloatField(null=True)
+    rfactor_min      = models.FloatField(null=True)
+    rfactor_max      = models.FloatField(null=True)
     segmentLength    = models.IntegerField()
     _querySet = None
 
@@ -70,6 +72,14 @@ class Search(models.Model):
         if self.resolution_max != None:
             query = query.filter(protein__resolution__lte=self.resolution_max)
 
+        # ...filter by rfactor...
+        if self.resolution_min != None:
+            query = query.filter(protein__rfactor__gte=self.rfactor_min)
+
+        # ...filter by rfactor...
+        if self.resolution_max != None:
+            query = query.filter(protein__rfactor__lte=self.rfactor_max)
+
         # ...filter by threshold...
         if self.threshold != None:
             query = query.filter(protein__threshold__lte=self.threshold)
diff --git a/pgd/pgd_search/search/SearchForm.py b/pgd/pgd_search/search/SearchForm.py
index cfaffd6..622fb49 100644
--- a/pgd/pgd_search/search/SearchForm.py
+++ b/pgd/pgd_search/search/SearchForm.py
@@ -47,6 +47,8 @@ class SearchFormBase(forms.Form):
     threshold       = forms.ChoiceField(choices=[(25,25),(90,90)], required=False)
     resolutionMin   = forms.FloatField(required=False, min_value=0, initial=0, widget=forms.TextInput(attrs={'size':3}))
     resolutionMax   = forms.FloatField(required=False, min_value=0, initial=1.5, widget=forms.TextInput(attrs={'size':3}))
+    rfactorMin      = forms.FloatField(required=False, min_value=0, initial=0, widget=forms.TextInput(attrs={'size':3}))
+    rfactorMax      = forms.FloatField(required=False, min_value=0, initial=0.30, widget=forms.TextInput(attrs={'size':3}))
     proteins        = forms.ModelMultipleChoiceField(queryset=Protein.objects.all().order_by('code'), required=False, widget=forms.SelectMultiple(attrs={'class':'field'}))
     proteins_i      = forms.IntegerField(required=False, widget=forms.HiddenInput(attrs={'class':'include'}))
     residues        = forms.ChoiceField(choices=[(i,i) for i in range(1, searchSettings.segmentSize+1)], initial=5)
diff --git a/pgd/pgd_search/search/views.py b/pgd/pgd_search/search/views.py
index 65c0fcf..6e8f81b 100644
--- a/pgd/pgd_search/search/views.py
+++ b/pgd/pgd_search/search/views.py
@@ -164,6 +164,8 @@ def processSearchForm(form):
     search.segmentLength = int(data['residues'])
     search.resolution_min = float(data['resolutionMin'])
     search.resolution_max = float(data['resolutionMax'])
+    search.rfactor_min = float(data['rfactorMin'])
+    search.rfactor_max = float(data['rfactorMax'])
     search.threshold      = int(data['threshold'])
 
     #save search object so its residue parameters can be added
@@ -221,6 +223,8 @@ def processSearchObject(search):
         'residues'      :search.segmentLength,
         'resolutionMin' :search.resolution_min,
         'resolutionMax' :search.resolution_max,
+        'rfactorMin'    :search.rfactor_min,
+        'rfactorMax'    :search.rfactor_max,
         'threshold'     :search.threshold
     }
 
diff --git a/pgd/pgd_search/templates/help.html b/pgd/pgd_search/templates/help.html
index 7cec4ce..c5097ac 100644
--- a/pgd/pgd_search/templates/help.html
+++ b/pgd/pgd_search/templates/help.html
@@ -56,6 +56,8 @@ Residues: How many residues are in the motif you want to search for?
 <br>
 Resolution: What resolution of crystal structures is searched?
 <br>
+R-factor: What R-factors of crystal structures are searched?
+<br>
 Threshold: This is the maximum sequence identity between any pair of proteins in the PGD (Hobohm et al., 1992)
 <br>
 <br>
diff --git a/pgd/pgd_search/templates/search.html b/pgd/pgd_search/templates/search.html
index ddf666e..46c34b0 100644
--- a/pgd/pgd_search/templates/search.html
+++ b/pgd/pgd_search/templates/search.html
@@ -370,6 +370,10 @@
                 <td>{{form.resolutionMin}} - {{form.resolutionMax}}</td>
             </tr>
             <tr>
+                <td class="label">R-factor</td>
+                <td>{{form.rfactorMin}} - {{form.rfactorMax}}</td>
+            </tr>
+            <tr>
                 <td class="label">{{form.threshold.label}}</td>
                 <td>{{form.threshold}}</td>
             </tr>