The effect of live Gumboro disease virus vaccination of 12 day-old chicks on their immune response to Newcastle disease vaccines was studied. The gumboro disease vaccinal virus had a suppressive effect on the immune response of chicks as measured by haemagglutinating inhibiting antibody titres and the protection rate using the challenge test. It can be concluded that the live Gumboro vaccinal virus has an immunosuppressive effect on the immune response of chicks to Newcastle vaccines.