Human parvovirus B19 infections have been linked with the development of a short-lived symmetrical polyarthritis and, rarely, a more persistent arthritis. We prospectively looked for serological evidence of recent B19 infection in 25 early synovitis patients presenting within 12 weeks of symptom onset and compared them with 21 controls seen over the same time period. None of the control patients had evidence of recent B19 infection while 3 of the early synovitis patients had raised IgM anti-B19 antibody levels. Two had a transient arthritis and 1 developed persistent seropositive rheumatoid arthritis.