Three subpopulations of light chains in Xenopus can be distinguished by monoclonal antibodies as well as by electrophoretic mobility on SDS-PAGE, peptide map and cell surface distribution. Analysis of these proteins from LPS-stimulated lymphocytes culture supernatants by two-dimensional gel electrophoresis showed a heterogeneity comparable to that observed for mouse kappa light chains. However, evidence from the selective expression of light chain subpopulations, as well as highly restricted light chain representation in anti-DNP antibodies, supports earlier findings that an antibody response in Xenopus is greatly limited in heterogeneity.