In a prospective study of recent arthritis, 103 patients had rheumatoid arthritis (RA), 63 seronegative oligoarthritis (SO), 67 reactive arthritis (REA), 20 ankylosing spondylitis (AS), and 13 psoriatic arthritis (PA). At the 8-year check-up, 36% of patients with RA were at work, compared with 69% in PA (p less than 0.002), and 85-90% in AS, SO, and REA (p less than 0.001). Correspondingly 43% of the RA patients were disabled by arthritis, compared with 23% in PA (NS), 15% in AS (p less than 0.005), none in SO, and 4% in REA (p less than 0.001). No significant differences in work capacity were noted between patients with PA, AS, SO or REA. In RA, the educational backgrounds of patients unable to work (44 patients) and able to work (37 patients) did not differ from each other or from the overall population of Finland, but a significantly (p less than 0.01) smaller number of patients with arduous work were able to continue at work. The mean age of 49 years for RA patients unable to work differed highly significantly (p less than 0.001) from the 35 years of RA patients at work. However, the weightiest cause of limited work capacity was severity of disease.