diff --git a/addons/website_crm_score/models/website_crm_score.py b/addons/website_crm_score/models/website_crm_score.py
index 23767e1002e..22c8854d204 100644
--- a/addons/website_crm_score/models/website_crm_score.py
+++ b/addons/website_crm_score/models/website_crm_score.py
@@ -41,6 +41,14 @@ class website_crm_score(models.Model):
     name = fields.Char('Name', required=True)
     value = fields.Float('Value', required=True)
     domain = fields.Char('Domain', required=True)
+    event_based = fields.Boolean(
+        'Event-based rule',
+        help='When checked, the rule will be re-evaluated every time, even for leads '
+             'that have already been checked previously. This option incurs a large '
+             'performance penalty, so it should be checked only for rules that depend '
+             'on dynamic events',
+        default=False
+    )
     running = fields.Boolean('Active', default=True)
     leads_count = fields.Integer(compute='_count_leads')
 
@@ -64,6 +72,13 @@ class website_crm_score(models.Model):
             where_clause += """ AND (id NOT IN (SELECT lead_id FROM crm_lead_score_rel WHERE score_id = %s)) """
             where_params.append(score['id'])
 
+            if not self.event_based:
+                # Only check leads that are newer than the last matching lead.
+                # Could be based on a "last run date" for a more precise optimization
+                where_clause += """ AND (id > (SELECT COALESCE(max(lead_id), 0)
+                                               FROM crm_lead_score_rel WHERE score_id = %s)) """
+                where_params.append(score['id'])
+
             self._cr.execute("""INSERT INTO crm_lead_score_rel
                                     SELECT crm_lead.id as lead_id, %s as score_id
                                     FROM crm_lead
diff --git a/addons/website_crm_score/views/marketing.xml b/addons/website_crm_score/views/marketing.xml
index fa8b554d2ab..be6ecae1601 100644
--- a/addons/website_crm_score/views/marketing.xml
+++ b/addons/website_crm_score/views/marketing.xml
@@ -80,6 +80,7 @@
                         <group>
                             <field name="value"/>
                             <field name="domain"/>
+                            <field name="event_based"/>
                             <field name="running"/>
                         </group>
                         <button name="assign_scores_to_leads" type="object" string=" Score Now" class="oe_link"/>
@@ -303,4 +304,4 @@
         <menuitem id="leads_dry_run" name="Assignation dry run" parent="leads_menu" action="lead_dry_run_action" groups="base.group_no_one"/>
 
     </data>
-</openerp>
\ No newline at end of file
+</openerp>