The frequency of arthropathy was evaluated in 251 patients with clinical and serological diagnosis (specific IgM detection by enzyme immunoassay) of exanthematous disease. Arthropathy (arthralgia and/or arthritis) was more frequent in dengue fever (49%) and rubella (38.2%) cases than in human parvovirus (30%) and measles (28.1%) cases. Except for measles cases, joint complaints prevailed in adults (> or = 15 years of age) and this difference was significant. The higher frequency of arthropathy in adults was more evident in human parvovirus (75%), rubella (65%) and dengue fever (57.7%) cases than in measles cases (31%). Arthropathy was also more frequent in females for all rash diseases studied. The results of this study showed the high occurrence of joint complaints in the disease described here and the importance of laboratory confirmation for their differential diagnosis.