The effect of orally given activated charcoal on the elimination of therapeutic and toxic doses of dapsone was studied in 5 healthy subjects and in 2 intoxicated patients. In a randomized crossover study the subjects took a total dose of 500 mg dapsone over 4 days; 10 hr after the last 100-mg dose of dapsone 50 gm activated charcoal as a water suspension (or water) was taken, followed by 4 consecutive doses of 17 gm at 12-hr intervals. The half-life (t 1/2) of serum dapsone was 20.5 +/- 2.0 hr during the control period and 10.8 +/- 0.4 hr during the charcoal period (p less than 0.01). The t 1/2 on serum monoacetyldapsone (MADDS) was shortened from 19.3 +/- 1.2 hr to 9.5 +/- 0.7 hr (p less than 0.01) by charcoal. The t 1/2s of dapsone and MADDS, calculated on the basis of urinary excretion rate, were shortened by charcoal; Two patients had taken large doses of dapsone in suicide attempts. The use of activated charcoal, 80 gm/day for 1 or 2 days, increased (3 to 5 times) the rate of elimination of both dapsone and MADDS, as reflected in serum concentration and urinary excretion data. The use of multiple doses of charcoal seems to be indicated as supplementary treatment of certain intoxications during the postabsorption phase if the drugs have a long t 1/2 and if they are secreted into the gut with subsequent reabsorption.