The organophosphorus nerve agents soman and tabun were tested in the hen at doses 120-150 times higher than their acute LD50, as it was assumed that these doses would produce delayed neuropathy. The animals were protected against the acute lethal effect of these agents by pretreatment with atropine, physostigmine, diazepam, and the oxime HI-6 or obidoxime. The surviving animals were followed for 30 days and the occurrence of delayed neuropathy was clinically diagnosed. Soman produced severe delayed neuropathy at a dose of 1.5 mg/kg, a dose which produced acute lethality in five animals out of six. Tabun elicited very mild neuropathic symptoms in one animal out of two at a dose of 6 mg/kg given on 2 consecutive days. Delayed neuropathy was not seen in the hens that survived the acute toxicity of a single dose of tabun , 12 mg/kg (three out of six) or 15 mg/kg (two out of six).