Experimental allergic orchitis is an organ-specific autoimmune disease characterized by inflammatory infiltrates associated with the seminiferous tubules of the testes. Orchitis is often, but not always, accompanied by aspermatogenesis in susceptible strains of mice. In this study, various strains of H-2 congenic mice were used to examine the relationship between orchitis and aspermatogenesis, and as a result, a genetic predisposition to spontaneous aspermatogenesis has been defined. A high correlation was seen between orchitis and aspermatogenesis in B10.D2/nSnJ mice, however, the two conditions were uncorrelated in C57BL/10J mice. Subsequent analysis of C57BL/10J congenic strains showed their aspermatogenesis to be spontaneous, rather than due to either testis-specific antigen or adjuvants. Further studies using other H-2 congenic strains revealed that the aspermatogenesis seen in C57BL/10J mice is linked to H-2 and influenced by C57BL/10J background genes. Finally, spontaneous aspermatogenesis was shown not to be a function of differences in the level of testicular testosterone.