To the Editor.— Kahn and Blum1 discuss the relationship between phenothiazines and the sudden infant death syndrome (SIDS) but do not mention the potentially important anticholinergic side effects of this group of drugs. Phenothiazines impair temperature regulation, including the ability to sweat, and are implicated in many reports of heatstroke2,3 and hypothermia. Any temperature rise tends to occur early in treatment4 and may bee provoked by standard dosage.5 Studies in mice given a single 1-mg/kg dose of chlorpromazine show that younger animals become hyperthermic, whereas older ones becomes hypothermic.6