1. This study elucidates the interaction of acute exercise and single ethanol intake on cholinergic enzyme and its relationship to lipid peroxidation in the blood and brain regions of the rat. 2. Butyrylcholinesterase (BuChE) in plasma and acetylcholinesterase (AChE) in brain regions as well as lipid peroxidation (MDA) were assayed in 1) sedentary control rats; 2) after acute exercise (100% VO2max); 3) ethanol 20% (1.6 gm/kg, p.o.); 4) exercise and then ethanol 20% (1.6 gm/kg, p.o.). 3. Acute exercise significantly increased BuChE activity (155% of control) in plasma and decreased AChE activity (60% of control) in the corpus striatum with a significant increase in the striatal MDA level (254% of control). Ethanol significantly decreased AChE activity only in striatum (86% of control) with a significant increase in striatal MDA level (132% of control). 4. The combination of exercise and ethanol 20% (1.6 gm/kg, p.o.) significantly increased BuChE activity (123% of control) in plasma, and decreased AChE activity (76% of control) in striatum with significant increase in striatal MDA level (147% of control). 5. Acute exercise, single ethanol 20% (1.6 gm/kg, p.o.) intake and the combination selectively inhibited striatal AChE, and the inhibition was correlated with increased lipid peroxidation indicating perturbation of motor function. The combination reduced the peripheral stress response caused by exhaustive exercise.