The alkaline elution method was used to examine genotoxic effects of MeIQ in various organs of rats after in vivo exposure. No DNA damage could be observed in the stomach, small and large intestine, liver, kidney or testis of male Wistar rats 2 h after a single intraperitoneal dose of 80 mg/kg MeIQ. In rats that had been pretreated with Aroclor 1254 (PCB), MeIQ induced significant DNA damage in the liver after both oral and intraperitoneal injection. MeIQ induced DNA damage in the large intestine, liver and kidney of male F344 rats given a single intraperitoneal dose of 80 mg MeIQ/kg or fed 0.03% MeIQ for 13 days. The DNA damage did not seem to accumulate during the feeding period.