In this study pure Aflatoxin B1 (AFB1) was given to broiler birds at the rate of 50, 100, 200, 400 and 800µg/kg feed for 28 days. Birds of experimental groups intoxicated with 50, 100 and 200µg/kg feed did not show any clinical and behavior alteration. Birds of experimental groups intoxicated with 400 and 800µg/kg showed depression, ruffled feathers and had decreased feed intake, increased water consumption with soft to watery feces. Birds fed 800µg/kg AFB1 for 28 days also exhibited nervous signs (torticollis). Mortality occurred in all treatment groups with the exception of those given 50 and 100µg/kg AFB1 for 28 days. Clinical signs and mortality percentages score increased with the increase in AFB1 levels. Dose related significantly decreased in relative organs weight were recorded in all groups with the exception of birds given 50 and 100µg/kg AFB1 for 28 days. Significantly increased scores of gross lesions were recorded with increasing dietary levels of AFB1. The present study concluded that, AFB1 at level of 50µg/kg feed did not show any behavioral, gross and pathological effect on broilers when fed continuously for 28 day. In other groups pathological changes were seen in dose related manner. Severe changes were seen in higher dose levels.