Over 8 million pounds of parathion [0,0-diethyl 0-(p-nitrophenyl)phosphorothioate], an organic phosphorous insecticide, are produced annually in the United States. Poisoning from parathion may follow its inhalation, cutaneous absorption, or ingestion. Most cases due to respiratory or cutaneous exposure are a result of the occupational hazard to workers involved in the preparation and use of parathion as an insecticide. Oral exposure usually occurs in cases of accidental poisoning (particularly in children), murder, and suicide, and only a very small amount of parathion is necessary to produce poisoning by this route. For example, a dose of 2 mg has been fatal to children from 5 to 6 years of age, and a dose of 120 mg was fatal to an adult.1Respiratory exposure to fine dusts or aerosols of parathion is hazardous but, because of the low vapor pressure of parathion, vaporization does not contribute significantly to the danger of