Atropine is often given as an antidote for acute cholinergic effects in studies of a delayed neuropathy (OPIDN) caused by some organophosphorus esters. These experiments examined if atropine would also affect the onset and/or severity of signs of OPIDN. Chickens were given one to six 200 micrograms/kg doses of diisopropyl phosphorofluoridate (DFP) with or without 20 mg/kg atropine (IM). Locomotion, brain neurotoxic esterase (NTE) activity, and histology of the nervous system were examined. The results demonstrated that atropine treatments delayed onset of the signs of OPIDN and may have slightly increased brain NTE activity in vivo. Relatively high levels (Ki: approximately 3.0 mM) of atropine inhibited NTE activity in vitro.