The effect of gold sodium thiomalate on adjuvant induced arthritis in DA rats was investigated. Ten mg/kg gold given in either weekly or daily injections before the administration of adjuvant was able to decrease the severity of arthritis in these animals. One mg/kg gold given as daily injections had no effect on adjuvant induced arthritis. One mg/kg gold given as weekly injections before adjuvant administration reduced the severity of arthritis to a level which was intermediate between that seen in the placebo control and the 10 mg/kg gold groups. The proliferative responses of spleen cells to mitogens in these animals were not altered by in vivo gold therapy.