The anticlastogenic activity of sodium-copper-chlorophyllin was tested against two known clastogens, chromium(VI) oxide and the pesticide chlordane, both of which occur as environmental toxicants. The chemicals were administered to male Swiss albino mice by gavage and chromosomes were studied from bone marrow cell 24 h after the exposure, following colchicine-air dying-Giemsa preparation. The end-points screened were the frequencies of chromosomal aberrations and damaged cells. The clastogenic effects induced by chromium in aqueous solution (20 mg/ kg body weight) were reduced to a significant level by chlorophyllin (1.5 mg/kg body weight), when administered both before and simultaneously with the toxicant. The effects of chlordane in olive oil (10 mg/kg body weight) were, however, not reduced by the administration of chlorophyllin (1.5 and 3 mg/kg body weight). © 1993.