Experiments were conducted to test the hypothesis that the hepatocarcinogenicity of di(2‐ethylhexyl) phthalate (DEHP) is due to its ability to produce DNA damage, either directly or as a result of the proliferation of peroxisomes and accompanying increased production of H2O2 and other DNA—damaging oxygen radicals induced by sustained exposure to the plasticizer. DNA repair, as assessed by the autoradiographic measurement of unscheduled DNA synthesis (UDS), was not observed in primary rat hepatocytes exposedin vitroto 10–5‐10–2 M DEHP orin vivoby a single gavage dose of 5 g DEHP/kg body weight administered 2, 15, or 24 h prior to the isolation of hepatocytes. Thus, DEHP does not appear to directly produce repairable DNA damage in rat hepatocytes.