This study was undertaken to assess the incidence and significance of autoantibody production following B19 infection, 53 patients with acute B19 infection (positive for serum anti-B19 IgM) were studied; symptoms were rash and arthralgia (n = 26), rash (n = 7), arthralgia (n = 16), aplastic crisis (n = 3), and intrauterine death (n = 1). These patients were followed for 26-85 months (mean 57 months) and re-assessed for persistent symptoms, serum anti-B19 antibodies, and serum autoantibodies. At follow-up, 14 test and two control patients had one or more serum autoantibodies (anti-nuclear antibody, anti-smooth muscle antibody, gastric parietal cell antibody, anti-reticulin antibody, anti-mitochondrial antibody, rheumatoid factor) at a titre of > or = 40 (P = 0.004). Seven test patients and no control patients had serum autoantibody at a titre > or = 160. Of these seven test patients, only one had persistent symptoms. At follow-up assessment, this woman was 48-year-old, had persistent arthralgia for 4 years following acute B19 infection, rheumatoid factor at a titre of 160 (1920 IU/ml), and had been independently diagnosed as having rheumatoid arthritis. In conclusion, results of the present study showed that low titre autoantibody production was common following symptomatic B19 infection, however, while interesting from a virological standpoint, this finding may be of little significance for future development of autoimmune disease.