OBJECTIVE The aim of this study was to investigate the occurrence and significance of hand deformities during the first 10 years of RA. METHODS One hundred and eighty-three early RA patients were included in the study during 1985-89. Mean +/- S.D. of age at onset was 51.4 +/- 12.4 years, and mean duration of symptoms before inclusion 12 +/- 7 months; 64% were women. The patients were followed annually. Assessment of hand deformities was standardized. Hand mobility was measured by signals of functional impairment (SOFI), disability by HAQ and hand HAQ, disease activity by ESR and radiographic changes by the Larsen method. RESULTS One hundred and eight (59%) patients developed at least one hand deformity during the study time. The majority occurred during the first years. After 10 years, the rate of ulnar deviation, button hole deformity and swan neck deformity was 44, 24 and 23.5%, respectively. The deformity group showed significantly higher disease activity during the first 5 years, and significantly more hand impairment, more disability and more severe radiographic changes throughout the study. Presence of a deformity after 1 year increased the risk of developing a Larsen score above median after 5 years. Odds ratio (95% CI) was 2.1 (1.023, 4.385). CONCLUSIONS More than half of the patients in this early RA cohort had developed hand deformities after 10 years. Most deformities occurred during the first year of the disease. Presence of hand deformities had an impact on daily life function and added useful prognostic information, being an early sign of a more severe disease.