Nepenthes alata is a tropical insectivorous plant with pitchers. After treating human red blood cells (RBCs) with the extract from the Nepenthes pitchers, the antigenicities of I, IF, Lud, and Om on the RBCs disappeared. As these antigens are associated with cold agglutinins, this extract appears to contain several decomposing enzymatic activities that work against glycolipids and glycoproteins. These activities of this extract, however, ceased on heating at 100 degrees C for 15 min.