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.evident that the crescentic paracostal laparotomy inc-ision wasthe most reliable approach to cholecystectomy operation in thedog through such approach it was easy to visullize, reach andmanipulate the gall bladder facilitatin~ its removal!Blunt dissection of the rectus adb abdominis and thetransverse abdomisis muscle parallel with their fibers, ~nsteadof their cutting, has illc.intaineci its antomic8.l fctioh. Inaddition, this procedure prevented severinc of crc:mia1 epigast-ric vessels. The caudal retraction of the iC~8stions ttiat wasproduced by raising the front part of the body, gIsatly faci1i-