The effects of soman (pinacolyl methylphosphonofluoridate) on coronary blood flow, the electrocardiogram, and cardiac function were measured in alpha-chloralose-anesthetized swine. Coronary blood flow (CBF), mean arterial blood pressure (MAP), peak systolic left ventricular pressure (IVP), maximum rate of left ventricular pressure development (dP/dtmax), cardiac output, and the ECG were monitored continuously. A dose of 2X LD50 of soman (1 LD50 = 4.6 micrograms/kg) was given at 1 LD50/min in the femoral vein, which produced an increase in coronary sinus plasma acetylcholine (ACh) from a control of 0.7 +/- 0.01 nmol/ml to a maximum 314% of control at 15 min and a decrease in CBF from a control of 99 +/- 13 ml/min/100 g to a minimum 55% of control at 15 min. The increase in ACh in the coronary sinus was significantly correlated with a decrease in CBF (r = -0.87, p < 0.001). The fall in CBF was accompanied by concomitant decreases in IVP, MAP, and dP/dtmax, with S-T segment elevation and ventricular fibrillation. The increase in coronary sinus acetylcholine concentration was significantly correlated with a 10-fold fall in coronary sinus acetylcholinesterase levels from a control of 2.47 +/- 0.97 mol acetylcholine hydrolyzed/ml blood/min and was consistent with the time course for the reduced hemodynamic measurements. These studies support the hypothesis that acetylcholine increases following soman toxicity may decrease coronary blood flow, thereby initiating ischemic electrocardiographic changes and reducing cardiac function.