Chickens surgically bursectomized (Bx) at 60 hours of incubation have been found unable to produce specific antibodies, in spite of close-to-normal serum immunoglobulin levels. Suppressor cell overactivity as a reason for the impaired antibody production in the Bx chickens has not been ruled out. In the present work, we have studied whether the state of immune unresponsiveness of the Bx chickens can be transferred to normal chickens by transfer of bone marrow cells. Bone marrow cells from 10-week-old Bx or control (Co) chickens were grafted into x-ray-irradiated histocompatible 5-12-day-old normal recipients. After the transplantation the recipients were immunized with a pool of five antigens, and the antibody responses were quantitated by ELISA. The inability of the Bx chickens to produce specific antibodies could not be transferred to normal chickens by transfer of bone marrow cells, as no differences in the antibody responses between the two recipient groups were observed. The results indicate that suppressor cells do not play a role in preventing specific antibody formation in the Bx chickens.