Ochratoxin A (OTA), a mycotoxin frequently present in food and feedstuffs, produces a wide range of toxic effects, including cell death via lipid peroxidation. In one human and four animal cell lines we determined the half lethal concentration (LC50) of OTA, its effect on reactive oxygen species (ROS) production, and its ability to induce cytochrome p450 activity. We also examined the protective effect of α-tocopherol and all-trans-retinol in the most sensitive cell lines (i.e. bovine mammary epithelia, for which LC50 was 0·8μg/ml (24h), and Madin Darby canine kidney, for which LC50 was 4·3μg/ml (48h)). Pre-incubation for 3h with either antioxidant significantly (P<0·05) ameliorated the OTA-induced reduction in cell viability and significantly decreased (P<0·05) ROS production. These findings indicate that oxidative stress is an important factor in OTA cytotoxicity. Supplementation with antioxidant molecules may counteract the short-term toxicity of this mycotoxin.