Eighty chickens (6 months old) were used in this work to evaluate the effect of the diethylnitrosamine (DEN). The chickens were equally divided into 4 groups (20 birds for each), 3 experimental and onecontrol. The experimental chickens were intramuscularlmg/kg B.wt. 3 times per week and for 2 months (gp. I), 4 months (gp. Il)or 6 months (gp. Ill). The mortality rates, clinical signs and pathologicalfindings were recorded.The mortality rates were 55%, 25% and 40% in the experimental chikckens of groups I, Il and IH, respectively. The chickens in all groups showed similar clinical signs. The latter included emaciation, depression, anorexia and rufled feathers beside sharp dThe liver, of the dead chickens in gp. (I and H) and the sacrificed chickens of gp. (I), was large, dark-red, friable and blood oozed from itscut-surfaces. Numerous grayish-white foci of about 1-2 mm. in diameterwere detected all over the hepatic surfaces.Microscopically, extensive replacement of the hepaticparenchymawithcoagulative necrosis, severe congestion of the portal blood vessels and the hepatic sinusoids beside hemorrhages and degenerative changes were observed. Lymphocytes aggregations in the int