Four live virus vaccines against Infectious Bursal Disease (IBD) were studied with regard to their safety, immune response and applicability. None of the vaccines caused clinical symptoms or had an adverse impact on bodyweight. Differences between these vaccines were observed in their effect on the Bursa/Bodyweight Ratio and the severity of the microscopical lesions of the bursa Fabricii. The immunosuppressive effect of IBD vaccination at one day of age on the response to Newcastle disease vaccine applied was rather low. Three of the four vaccines induced antibodies associated with protection against challenge. Vaccination of SPF rearing chickens by drinking water at an age of 15 weeks produced an antibody response (Agar Gel Precipitin Test) whereas at 15 weeks produced an antibody response (Agar Gel Precipitin Test) whereas at an age of 23, 32 and 60 weeks it did not. Chickens of all age groups responded serologically to an intramuscular vaccination. A correlation was found between the immunological response and the effect of the vaccines on the bursa Fabricii.