ABSTRACT. Three patients were treated after ingestion of an overdose of dapsone (1–10 g). A considerable acute cyanosis due to methaemoglobinaemia was followed by a late haemolysis within 1–2 weeks. Activated charcoal given orally in multiple doses (20 g × 4/day) shortened the half-life of dapsone to 12.7+0.7 hours, i.e. to about 1/3-1/6 of the preceding control value. The half-life of dapsone was about 10 hours during each of the three 5-hour haemodialysis treatments given to one patient. However, owing to the rebound phenomenon between haemodialyses, the half-life of dapsone from the start of the first to the end of the third haemodialysis was 26 hours. The efficacy of orally administered activated charcoal is fully comparable to that of haemodialysis in increasing the rate of elimination of dapsone and its metabolite monoacetyldapsone. Activated charcoal is cheap, it can be administered anywhere and its administration rarely involves complications.