The occurrence of pupillary constriction in children comatose as a result of the acute ingestion of common drugs has been studied in a large pediatric hospital by reviewing records of patients admitted between 1965 and 1974. Among 94 patients with an acute drug ingestion, the frequency of miosis in relation to the cause of coma was 88% for narcotics, 72% for phenothiazines, 35% for ethanol, and 31% for barbiturates. In contrast, miosis was noted in only 3% of 105 patients with coma from head injuries or infection of the central nervous system. Miosis was associated with all four drug ingestions among patients in deep coma and with narcotic and phenothiazine ingestions among patients in light coma. The frequency of miosis was found to increase with increasing depth of coma in patients with all four drug overdoses, particularly among patients with phenothiazine and barbiturate ingestions.