A method was established to detect clonal lambda light chain gene rearrangements in peripheral blood lymphocytes and frozen or paraffin-embedded tissues. V lambda-gene-family-specific primers were used together with a J lambda primer mix in separate reactions to amplify V lambda gene rearrangements by the polymerase chain reaction. Clonal lambda gene rearrangements were detected in seven of seven lambda-expressing B cell leukemias, in four of five lambda-expressing non-Hodgkin's lymphomas with frozen tissues, and in seven of nine cases of lambda-expressing non-Hodgkin's lymphomas for which formalin-fixed, paraffin-embedded specimens were available. Clonality of amplified polymerase chain reaction products was confirmed by sequence analysis for several cases. The present study shows that it is possible to amplify clonal lambda gene rearrangements in the majority of lambda-expressing B cell leukemias and lymphomas. The method described here, therefore, is a useful supplement to the previously described approach of VH and VK gene amplification to detect clonal B cell populations and allows the study of V lambda gene usage and somatic mutation in lambda-expressing normal and malignant B cells.