The indolent follicular and diffuse lymphomas are neoplasms of B-cell origin. In several other B-cell neoplastic disorders, including multiple myeloma, hairy cell leukemia, and chronic lymphocytic leukemia, the light chain isotype of the surface immunoglobulin has been reported to have prognostic significance. Patients with tumors expressing lambda light chains usually fare more poorly than those with kappa light chain-bearing tumours. We analyzed the clinical data and immunologic phenotype of 101 patients with indolent lymphoma. Eighty-nine of the 101 patients demonstrated surface immunoglobulin of only one light chain type (kappa-47, lambda-42). Patients in both groups were matched for known prognostic factors. There were no significant differences in disease-free survival or overall survival between the two groups or within histologic subtypes. These results indicate that the immunologic light chain phenotype in indolent lymphoma, unlike other B-cell neoplasms, is not a prognostic indicator of survival.