The existence of two types of the immunoglobulin (Ig) light chain in pigs was documented>30 years ago and has been confirmed by the cloning of porcine light chain genes homologous to human and murine Ig kappa (Igkappa) and Ig lambda (Iglambda). However, immunochemical reagents defining these two light chain isotypes have not been characterized. Here, we show that rabbit antisera specific for human Igkappa and Iglambda and certain anti-porcine light chain monoclonal antibodies (mAb) are useful in distinguishing light chain isotypes by flow cytometry (FCM). Porcine B cell lines L23 and L35 stained positive only with anti-human Iglambda antiserum and were negative when tested using anti-human Igkappa antiserum. While mAbs K139.3E1, 1G6 and 27.7.1 also tested positive on these cell lines, mAb 27.2.1 did not. Therefore, FCM was used to examine the hypothesis that K139.3E1, 1G6 and 27.7.1 are Iglambda-specific whereas mAb 27.2.1 recognizes the Igkappa chain in pigs. Double staining of peripheral blood mononuclear cells (PBMC) with pairs of anti-light chain mAbs and using cocktails of anti-light chain mAbs and anti-human polyclonal antiserum, confirmed this hypothesis with the exception that mAb K139.3E1 appears to recognize only a subset of Iglambda(+) B cells in most pigs. In summary, we identified two pan-specific anti-pig Iglambda mAbs, one anti-lambda mAb that recognizes a lambda-light chain subset and one anti-pig Igkappa mAb.