White leghorn hens (S/group) received 500 or 2000 mg/kg of undiluted cresyl diphenyl phosphate (CDP) (test groups), 500 ag/kg of a 25% preparation of tri-o-toly1 phosphate in corn oil (positive control group) or corn oil only (vehicle control group) as a single oral dose on day-0 of the study. Clinical signs were recorded daily. Body weights were recorded.on day 0 and day 2. Animals were sacrificed at termination on day 2 and underwent gross necropsies. Neurotoxic esterase (NTE) measurements of brains and spinal cords and cholinesterase measurements of the brains were recorded. No neuropathology was performed. No deaths occurred; all animals survived until study termination. .No clinical signs were noted in any hen during the study. No significant differences in body weights were noted when comparing the test or the positive control groups to vehicle control. No significant differences in brain cholinesterase measurements were noted when comparing the test or positive control animals with vehicle controls: Brain NTE measurements were reduced 694 and 89% among hens receiving 500 and 2000 mg/kg of CDP, respectively, when compared to vehicle control bens; positive control hans displayed 86% reduction in brain NTE levels when.compared to vehicle control hens. Spinal cord NTE levels were reduced 644 and 100% among bens receiving 500 and 2000 ag/kg of CDP, respectively, when compared to vehicle control hens; positive control hens displayed an 814 reduction in spinal cord NTE levels when compared to positive control hens.