The focus of this study was to assess the cardiovascular effects in hens of a single 2.5 mg/kg intramuscular injection of phenyl saligenin phosphate (PSP) into the breast muscle. Parameters were measured at 1, 3, 7, and 20 days post treatment. All hens developed clinical signs of delayed neuropathy by day 10 and these signs were maximal by day 20. Alterations of measured parameters were observed prior to the onset of clinical signs of organophosphorus-induced delayed neuropathy (OPIDN) (days 1, 3, and 7) as well as when maximal clinical signs were evident (days 15-21). Significant decreases in the activities of brain NTE and plasma cholinesterase as well as decreases in weight and the level of pcO2 and an increase in peripheral resistance were observed prior to evidence of clinical signs of OPIDN. When maximal signs of OPIDN were present, brain NTE and plasma cholinesterase were at control levels but brain cholinesterase was significantly increased. Significant decreases in body weight and arterial pCO2 and significant increases in limb venous flow, arterial blood pressure, and hematocrit were seen at this time. / Master of Science