Dapsone given over 14 weeks in a dose of 50 mg a day for 1 week and thereafter 100 mg a day was found to have a beneficial effect in rheumatoid arthritis when compared with placebo administration to a matched group of patients. Significant improvement in 5 out of 7 clinical measurements and in erythrocyte sedimentation rate, viscosity, C-reactive protein was found in those patients taking dapsone. There was significant improvement compared to the placebo group in 2 out of the 7 clinical measurements and again in all 3 acute-phase reactants. The drug was quite well tolerated over the 14-week duration of the trial. The tendency to cause haemolysis will be its main limiting factor as a practical alternative to other suppressive agents currently in use.