A population of lymphocytes bearing a membrane receptor for antigen-antibody-complement (Ag-Ab-C) complexes was identified. These lymphocytes, called complement receptor lymphocytes (CRL), bind EAC (erythrocytes sensitized with antibody and complement) and form rosettes. This binding is C3-dependent and is distinct from non-CRL lymphocytes. CRL can be specifically depleted from lymphoid cells using ultracentrifugation in a BSA gradient, as CRL have a higher density than free lymphocytes. CRL and non-CRL differ in their ability to bind to nylon wool, with CRL adhering more strongly. CRL also contain most of the lymphocytes bearing immunoglobulin (Ig) determinants on their membranes. CRL are not found in the thymus but are present in spleen, lymph nodes, and other lymphoid organs. CRL are not found in plaque-forming cells from mice immunized with heterologous red cells, suggesting they may not be precursors of antibody-secreting cells. CRL and non-CRL have different distributions among lymphoid organs, with CRL being more abundant in spleen and lymph nodes. CRL may play a role in antigen localization and immune response by binding Ag-Ab-C complexes. The presence of a complement-dependent receptor on some lymphocytes may be related to their function in antigen recognition and immune response. The study shows that CRL and non-CRL are distinct subpopulations of lymphocytes with different properties and distributions.A population of lymphocytes bearing a membrane receptor for antigen-antibody-complement (Ag-Ab-C) complexes was identified. These lymphocytes, called complement receptor lymphocytes (CRL), bind EAC (erythrocytes sensitized with antibody and complement) and form rosettes. This binding is C3-dependent and is distinct from non-CRL lymphocytes. CRL can be specifically depleted from lymphoid cells using ultracentrifugation in a BSA gradient, as CRL have a higher density than free lymphocytes. CRL and non-CRL differ in their ability to bind to nylon wool, with CRL adhering more strongly. CRL also contain most of the lymphocytes bearing immunoglobulin (Ig) determinants on their membranes. CRL are not found in the thymus but are present in spleen, lymph nodes, and other lymphoid organs. CRL are not found in plaque-forming cells from mice immunized with heterologous red cells, suggesting they may not be precursors of antibody-secreting cells. CRL and non-CRL have different distributions among lymphoid organs, with CRL being more abundant in spleen and lymph nodes. CRL may play a role in antigen localization and immune response by binding Ag-Ab-C complexes. The presence of a complement-dependent receptor on some lymphocytes may be related to their function in antigen recognition and immune response. The study shows that CRL and non-CRL are distinct subpopulations of lymphocytes with different properties and distributions.