Cells from chickens bursectomized at 60 hr of incubation (Bx) and normal controls (Co) were assessed for the ability to secrete immunoglobulins and specific antibodies in vitro. Anti-tetanus antibodies were observed in the culture supernatants of cells from tetanus-immunized Co chickens. Cells from immunized Bx and nonimmunized Co chickens did not secrete specific antibodies. Cells of both Bx and Co chickens secreted similar amounts of immunoglobulins (IgM, IgG, IgA). Antigenic stimulation in vitro had no effect on the secretion of specific antibodies or on cell proliferation; this applies for Bx and Co chickens. To test whether antigenic stimulation in vitro together with adherent cells would induce antibody production in Bx cells, cocultures of peripheral blood adherent cells and lymphocytes from spleen or peripheral blood were used. Culture of lymphocytes with histocompatible and allogeneic adherent cells, with or without antigenic stimulation, did not enhance secretion of anti-tetanus antibodies from cells of Bx chickens. The adherent cells increased the secretion of total immunoglobulins, of all classes, by both Co and Bx cells alike. They also enhanced the secretion of specific antibodies by Co cells. These findings indicate that the functional failure of Bx lymphoid cells cannot be corrected by better antigenic presentation.