Three new cytotoxic H-2 specificities are defined. H-2.37 is present in alleles f, p, and pa; H-2.38 in alleles p, pa, and w; and H-2.39 in alleles b, f, and i. The first two specificities have appeared in a number of antisera and, in every case, were without hemagglutinating activity. H-2.39 was very weakly hemagglutinating in one antiserum, nonhemagglutinating in another. The presence of 39 in allele b and the crossover-derived i and its absence from crossover h places 39 at the K end (although not necessarily in the K region) of the H-2 crossover map.