Shortly SHORTLY after the antimalarial activity of the parent sulfone dapsone was discovered, the drug was discarded as too toxic for human use.1-4 This occurred at the time when it was assumed that the amount of sulfone necessary for treatment was similar to that used with the sulfa drugs, ie, 1 to 2 gm daily. As a result, total doses of 36 and 16 gm of dapsone were administered over periods as short as nine days in the first human trials of dapsone as an antimalarial agent.5,6 In both clinical trials, dapsone was effective against Plasmodium falciparum, but later reports of its toxicity1-4 and the successful introduction of the 4-aminoquinoline drugs led to abandonment of dapsone as an antimalarial drug. In 1949, dapsone was introduced for the treatment of leprosy,7 and soon after small daily doses of dapsone were found to be therapeutically effective and relatively non-toxic (ie, 100 mg or