The effects of daily chronic treatment for 6 months with pravastatin was evaluated on the performance of the skeletal muscle system of different rat groups. At all doses (0.1 mg/kg-20 mg/kg) the righting reflex and the electromyographic signals observed in vivo did not show any abnormality. At the end of the treatment the Extensor digitorum longus muscles were dissected from treated and control rats and their passive and active electrical parameters were analyzed in vitro by standard microelectrodes technique. Pravastatin did not modify the chloride conductance nor the excitability characteristics of the fibers. Chronic treatment with pravastatin does not produce any alteration of skeletal muscle function.