Intraperitoneal injection of pristane (2,6,10,14 tetramethylpentadecane) is a standard technique for obtaining monoclonal antibody-enriched ascitic fluid. However, pristane also induces plasmacytomas and an erosive arthritis resembling rheumatoid arthritis in BALB/c mice, probably as a consequence of enhanced interleukin 6 production. We report here that the production of autoantibodies characteristic of systemic lupus erythematosus (SLE) is a further consequence of injecting pristane in BALB/c mice. Anti-Su antibodies appeared as early as 1-2 mo after a single injection of 0.5 ml pristane, followed by anti-U1RNP and anti-Sm antibodies after 2-4 mo. Within 6 mo of pristane injection, 9 of 11 BALB/c mice had developed anti-Su, anti-U1RNP, anti-U2RNP, anti-Sm, and possibly anti-U5RNP antibodies. Autoantibodies were not produced by 20 BALB/c mice of the same age and sex that were not injected with pristane. Thus, autoantibodies characteristic of lupus were induced in mice that are not usually considered to be genetically susceptible to the disease. The induction of autoantibodies associated with SLE by pristane may be relevant to understanding the role of abnormal cytokine production in autoantibody production and the pathogenesis of autoimmune disease. Furthermore, the induction of high titer autoantibodies by pristane dictates caution in the use of ascitic fluid as a source of monoclonal antibodies, since the polyclonal antibodies induced by pristane may copurify with the monoclonal antibody secreted by an injected hybridoma.