Bovine lymphosarcoma cells grown in tissue culture were examined for the presence of surface immunoglobulins. The experimental criterion employed was the specific binding of 125I-labeled antibody directed to bovine immunoglobulin determinants. It was noted that lymph node cell suspensions and peripheral blood leucocytes from a lymphosarcomatous animal exhibit specific binding of rabbit antibody directed to such determinants. However, thymocytes from such an animal fail to bind antibody. Normal peripheral blood leucocytes also show specific binding of rabbit anti-BγG and anti-µ chain antibody. It is also apparent that tissue culture cells adsorb exogenous immunoglobulin by exposure to equine serum and bovine serum. Tissue culture cells grown in medium containing 10% rabbit serum, however, exhibit BγG-like determinants. They clearly bind anti-BγG antibody but this binding does not seem to involve Fc determinants of the γ chain. Anti-µ chain antibody is not specifically bound and the binding of anti-γ chain antibody is ambiguous. It appears, however, that there are at least L chain determinants on the cell surface.