A decreased antibody response to injected sheep red blood cells and weight losses to the extent of 25-38% were observed in the bursa Fabricii and thymus in chicks fed an aflatoxin diet (10% w/w) for 3 weeks. The immune organs did not show any significant histopathological changes. The antibody titre decreased from day 6 of treatment onward until the 15th day, when the antibody titre had disappeared completely in the test chicks. The body weight gain was also less in test chicks (9.7-37.3%) given test feed or test feed along with Salmonella pullorum in water (10(8) cfu ml 1) in comparison to chicks given toxin-free diet and water after 3 weeks of feeding trials. The disappearing component in the test chicks' liver homogenate was found to be antigenic by immunoelectrophoretic studies.