Lactoperoxidase-catalyzed cell surface radioiodination was employed to label membrane proteins of chicken cells from bursa, and spleen cells from normal or bursectomized (Aγ) chickens. Detergent lysates of labelled cells were precipitated with rabbit anti-chicken Ig Fab antisera to isolate membrane immunoglobulins and with chicken anti-human gamma globulin: human gamma globulin immune complexes or insoluble, heat-aggregated chicken Ig to isolate Fc receptors (FcR). Resolution of bursa or normal spleen cell membrane proteins bound by anti-Fab antibodies by SDS-PAGE under reducing conditions revealed three molecular species (70,000, 45,000 and 25,000 dallons) specifically precipitated. All membrane proteins bound by the anti-Fab reagents were bound by antisera specific for chicken IgM. Bursa lymphocyte membrane proteins which bound to immune complexes were resolved into two major molecular species (55,000 and 45,000 daltons). The 45,000-dalton FcR exhibited an isoeleclric point and detergent sensitivily idenlical to a 45,000-dalton protein coprecipitated with membrane Ig. Two-dimensional gel analysis of Fc receptors obtained from spleen cells of bursectomized birds revealed that these proteins can be distinguished by size and/or charge from bursa Fc receptors. The results suggest that chicken lymphocyte Fc receptors comprise a group of proteins which can be distinguished by size, charge, and cellular origin.