Mice, homozygous for thenugene (nudemice), have no capacity for rejection of allografts as evidenced by this study of nine different graft‐host combinations. The mice concerned stem from an intermediate stage in anugene transfer to three inbred strains (BALB/c, C3H, C57/BL). Mice of each of the three genetic backgrounds accepted skin grafts from three inbred donor strains, differing at the H‐2 locus. A preliminary comparison with a concurrent study of heterografts (rat skin) indicates that allografts are not so readily incorporated, and are more prone to endogenous damage during the take process. This paradoxical observation is discussed at greater length in the subsequent article on heterotransplants innudemice. After allografting,nudemice display lymphocytosis, and there is lymphoid cell proliferation in the primary follicles of lymph nodes, and increased numbers of mononuclear cells are seen in the paracortex of lymph nodes and in the red pulp of the spleen. No cytotoxic alloantibodies could be demonstrated in serum from the graft bearingnudemice. Thymus grafting confers capacity for allograft reject