A case of nonfatal, acute poisoning following the ingestion of an undetermined amount of dapsone (DDS) in a 49-year-old woman is presented. The clinical features were dyspnea and deep cyanosis. Methemoglobinemia was 39.0% on admission. DDS was identified and quantitated in blood samples taken on the third day (sample A) and fifth day (sample B) in the hospital using a high-performance liquid chromatographic technique with diode-array detection. DDS concentrations were 26.99 and 8.40 micrograms/mL in samples A and B, respectively. Results are discussed in the light of an extensive review of the literature (1950-1993) available on DDS poisonings.