DIISOPROPYL fluorophosphate ("DFP") has been shown to have a marked and prolonged miotic effect in normal men and animals.1 The miosis may be accompanied with spasm of accommodation and ciliary pain.2 These effects have been shown to be due entirely to the inactivation of cholinesterase and not to direct action on the iris and ciliary muscle.3 In this respect "DFP" is similar to physostigmine4 and neostigmine,5 but in its reaction with cholinesterase it is at least five and a half times as potent and much more persistent than physostigmine.6 "DFP" can also overcome the effects of atropine and homatropine on the pupil and ciliary muscle.3 Finally, "DFP" has been shown to resemble physostigmine in its influence on the intraocular tension of normal human eyes,1h differing, however, in that its effect is much more prolonged. Occasional normal human eyes show a rise in