SUMMARYAutologous bursal implants located within the peritoneal cavity did not repair the deficiencies in germinal center production or primary antibody responsiveness of chickens bursectomized at hatching. Similarly, bursal implants had no effect on the hypermacroglobulinemia of bursectomized birds. Serial observation of bursal implants revealed early central necrosis, followed by vascularization and subquent morphological and functional integrity of bursal epithelium. Continued lymphopoiesis was not observed in bursal implants; the lymphoid follicular nature of the bursa was entirely lost within the first few days following implantation. Thymus implants exhibited early central necrosis but redeveloped normal lymphoid architectural features in the same peritoneal location. It is postulated that proximity to the contents of the intestinal lumen is essential to the special lymphopoietic functions of the bursa.