Caffeic acid phenethyl ester (CAPE) is an antioxidant that can scavenge free radicals and protect cellular macromolecules, including DNA and proteins, from oxidative damage induced by various agents. The protective effect of CAPE on cisplatin-induced chromosome aberrations has been determined in rat bone marrow cells. The animals were pretreated with a single dose of CAPE (10 mmol/kg body weight [b.w.]) injected intraperitoneally (i. p.) 24 hours before the administration of cisplatin and then sacrificed 24 hours after the cisplatin administration. Cisplatin was administered to rats either alone (5 mg/kg b. w., i. p.) or after CAPE treatment. CAPE has led to a statistically significant decrease in the total number of chromosomal aberrations and abnormal metaphases induced by cisplatin when compared with only cisplatin given groups. We have concluded that CAPE could prevent cisplatin-induced chromosome aberrations by establishing a potent free radical scavenger effect.