diff --git a/src/main/scala/ALSAlgorithm.scala b/src/main/scala/ALSAlgorithm.scala
index 7c0ddb9..62f87a3 100644
--- a/src/main/scala/ALSAlgorithm.scala
+++ b/src/main/scala/ALSAlgorithm.scala
@@ -158,6 +158,7 @@
         i = i,
         items = model.items,
         categories = query.categories,
+        categoryBlackList = query.categoryBlackList,
         queryList = queryList,
         whiteList = whiteList,
         blackList = blackList
@@ -218,6 +219,7 @@
     i: Int,
     items: Map[Int, Item],
     categories: Option[Set[String]],
+    categoryBlackList: Option[Set[String]],
     queryList: Set[Int],
     whiteList: Option[Set[Int]],
     blackList: Option[Set[Int]]
@@ -232,6 +234,12 @@
         // keep this item if has ovelap categories with the query
         !(itemCat.toSet.intersect(cat).isEmpty)
       }.getOrElse(false) // discard this item if it has no categories
+    }.getOrElse(true) &&
+    categoryBlackList.map { cat =>
+      items(i).categories.map { itemCat =>
+        // discard this item if has ovelap categories with the query
+        (itemCat.toSet.intersect(cat).isEmpty)
+      }.getOrElse(true) // keep this item if it has no categories
     }.getOrElse(true)
   }
 
diff --git a/src/main/scala/Engine.scala b/src/main/scala/Engine.scala
index 766f7d8..034935a 100644
--- a/src/main/scala/Engine.scala
+++ b/src/main/scala/Engine.scala
@@ -7,6 +7,7 @@
   items: List[String],
   num: Int,
   categories: Option[Set[String]],
+  categoryBlackList: Option[Set[String]],
   whiteList: Option[Set[String]],
   blackList: Option[Set[String]]
 ) extends Serializable