A motor polyneruropathy developed in a woman with subcorneal pustular dermatosis of 16 yr duration, who had received at least 300 g of dapsone over a 5-yr period and 80 g during the 4-mo. period of progression of her neurologic symptoms. Although the patient believed her muscle power had returned to normal 4 mo. after the drug was stopped, a slight peripheral neuropathy remained. Electrodiagnostic and clinical features during the period of greatest weakness and the subsequent 16 mo. were consistent with a polyneuropathy of dapsone appears to be dose-dependent, but the mechanism by which it occurs is unknown.