Fish-oil derived n-3 PUFA such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) has been shown to exhibit anti-carcinogenic effects in vivo and in vitro. Squalene, found in shark liver oil and olive oil, can effectively inhibit chemically induced tumorigenesis in rodents. The aim of the present study was to investigate whether supplementation with EPA (50 mumol/L), DHA (50 mumol/l) or squalene (50 mumol/l) for 24 It would protect Chinese hamster V79 fibroblast cells against oxidant-induced DNA damage. EPA and DHA were delivered to the cells either complexed to bovine serum albumin (BSA) or dissolved in ethanol. DNA damage was assessed using the sister chromatid exchange (SCE) assay. V79 cells exposed to hydrogen peroxide (H2O2) alone showed a significant increase in SCE (P < 0.05) when compared with control levels. Pre-incubation with either EPA or DHA did not significantly affect H2O2-induced SCE regardless of the delivery vehicle employed. However, pre-treatment with squalene significantly decreased the frequency of SCE induced by H2O2 (P < 0.05). Results indicate that squalene was more effective than EPA and DHA in protecting against H2O2-induced SCE. (C) 2002 Elsevier Science Inc. All rights reserved.