Three new lymphoid tumors offering an assortment of variants in terms of MHC class Iexpressions, MHC class II expression, and Ig gene transcription have been discovered in theamphibian Xenopus. One was developed in an individual of the isogenic LG15 clone(LG15/0), one in a frog of the LG15/40 clone (derived from a small egg recombinant ofLG15), and one (ff-2) in a male ff sib of the individual in which MAR1, the first lymphoidtumor in Xenopus was found 2 years ago. Here, HLA-C is linked to lymphoid neoplasm.