The herbicide pendimethalin (STOMP) shares a similar chemical structure with nitro compounds such as dinitrobenzene, which was previously demonstrated to cause methemoglobinemia in mammals. However, reports on STOMP poisoning in humans are rare. We reviewed 71 STOMP poisoning cases (42 men and 29 women of mean age 43.9 +/- 2.5 y) reported to the Poison Control Center--Taiwan from September 1986 to September 1997 and summarized their clinical manifestations. Two incidences resulted from skin and eye contact. The rest were due to oral ingestion intentionally or accidentally. The average ingestion was 106.1 +/- 13.4 ml. Among them, 20 cases had no symptoms or signs, 38 had mild effects such as nausea, vomiting and sore throat, 7 had effects such as severe retching, hematemesis and seizures. Four patients expired due to also taking other herbicides (mainly organophosphates) and because of inadequate airway management. Adequate ventilation support was the major therapy in salvaging the poisoning cases.