Stimulation of lysosomal activity and ROS formation in mouse peritoneal macrophages by five triterpene glycosides, typicosides A1 (1), A2 (2), B1 (3), C1 (4) and C2 (5) has been studied and compared with their cytotoxic activities. Glycosides 1-3 possess moderate activities, but the most cytotoxic glycoside 5 is not active. Typicoside C1 (4), with low toxicity, was proved to be the most active concerning stimulation of ROS formation. This is the first example of a triterpene glycoside from sea cucumbers with low cytotoxicity, but which demonstrates a strong immunostimulatory effect on mouse peritoneal macrophages in vitro.