A 12-month double-blind controlled study comparing hydroxychloroquine 400 mg daily with placebo in 104 patients with mild RA was conducted to see whether patients with mild rheumatoid arthritis (RA) benefit from treatment with diseasemodifying agents. Mild RA was defined as synovitis limited to the hands and feet, an ESR <30 mm/h and C-reactive protein <20 mg/l, a situation where accepted clinical practice is to use a non-steroidal anti-inflammatory agent alone. By 6 months, the improvement of clinical and laboratory parameters in the hydroxychloroquine treated patients was significant compared with pretreatment levels and significantly greater than the control group. This improvement was maintained at 12 months. In addition, fewer patients withdrew through lack of efficacy, eight on hydroxychloroquine versus 18 on placebo. The implications of treating this well defined group of patients is discussed.