Two men were accidentally exposed to vapors of sarin, a cholinesterase inhibitor and extremely toxic nerve gas. Diagnosis was confirmed by depressed cholinesterase activity, and fixed extremely miotic pupils. No other signs or symptoms developed and neither man required treatment. Recovery to normal cholinesterase activity was gradual over a 90-day period. Pupillary reflexes were not detectable until 11 days after exposure; the miotic pupils dilated slowly over a 30-45 day-period. Eye pain and blurred vision did not occur; visual acuity and amplitude of accommodation were improved for several weeks. Other functions not affected significantly were intraocular pressure, visual fields, color vision, heterophorias, and vergences.