Cyclamin, a monodesmosidic triterpenoid saponin isolated from the tubers of Cyclamen purpurascens Mill. was found to possess molluscicidal activity against the schistosomiasis-transmitting snail Biomphalaria glabrata (Say). The lowest concentration showing 100 % mortality to snails was 21 mg/l. The haemolytic activity and the molluscicidal potency of cyclamin were comparedwith those of primulic acid with the result that high haemolytic activity will not automatically imply a strong molluscicidalpotency.