The incidence of antinuclear antibodies after Rauscher leukemia virus inoculation was significantly higher in C57BL/6 than in BALB/c mice and still greater in their F1 hybrids. The relationships among antinuclear antibody incidence, erythroblastic disease, Rauscher leukemia virus production and the H-2 genotypes were studied in the F1 generation and backcrosses using different virus inocula. At least 2 genes may be involved in the control of susceptibility to Rauscher leukemia virus-induced erythroblastosis, 1 of them probably being H-2 linked. A non-H-2 linked gene seems to control, at the same time, induction of antinuclear antibodies, focus-forming virus production in the spleen and susceptibility to the disease. C-type viruses apparently play an active role in antinuclear antibody induction.