1. There were no changes suggestive of SLE in the rabbits that had received hydralazine in daily dossage of 200mg per kilogram body weight for as long as 4 months. 2. Of the rabbits sensitized with egg white and, in addition, administered with hydralazine, many died suddenly after injections of egg white, but a few rabbits showed anemia, probably hemolytic in type. No LE cell phenomenon or antinuclear factor (ANF) was revealed in this group. 3. Slight leucopenia, albuminuria, hypergamma-globulinemia and increased IgG were found in the rabbits injected with rat anti-rabbit cell nuclei serum. Four rabbits showed nephritis, productive in form at necropsy, with deposition of γ-globulin in glomerular capil laries as revealed by the direct FAT. Weak LE cell phenomenon and ANF were positive in one rabbit. 4. It is presumable that, as in human cases, hereditary factor is impcrtant to produce the models of auto-immune diseases in animals.