We have investigated the generation of a prooxidant state and effect on prostaglandin E (PGE) levels after administration of diethylnitrosamine (DENA) to rats. Lipid peroxides were assayed by monitoring thiobarbituric acid (TBA) a reactive material. PGE - like activity was assayed by using bioassay procedure. Our results demonstrate that increased lipid peroxide and decreased PGE levels were found in a dose dependent manner in DENA injected groups when compared to control groups. According to these findings, it is suggested that there is a negative correlation between carcinogenic DENA induced lipid peroxidation and PGE in rat's liver, lung, and renal tissue.