Abstract: The postmortem and serological investigations of poultry diseases were conducted in different farms of Bangladesh. A total numbers of 1653 either dead or sick birds were examined. The incidence of aflatoxicosis was highest (27.59%) followed by nutritional deficiency (12.40%), infectious bursal disease (11.80%), chronic respiratory disease (8.11%) newcastle disease (7.50%) salmonellosis (5.56%) colibacillosis (4.42%), fowl cholera (3.08%) were found. 5.32% cases remain undiagnosed due to lack of diagnostic facilities or autolysis of the bird. In sero-evaluation, commercial and native birds were found 93-97, 80 -55, 56-12, 60-73, 67-61 and 22-3% sero-positive for newcastle disease, infectious bursal disease, pullorum, M. galisepticum, M. synovie and chicken infectious anemia respectively.