Simvastatin is a potent inhibitor of hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase intended for use as a hypocholesterolemic agent. The long-term clinical experience with simvastatin indicates that it is a safe, effective, and well-tolerated hypolipidemic agent. Laboratory adverse events involving elevations of serum transaminase levels and serum creatine kinase (CK) levels to more than three times the upper limit of normal range have been seen in 1.5% and 3.4% of cases, respectively. We describe a case of severe myopathy and rhabdomyolysis associated with concomitant use of simvastatin and gemfibrozil. Seven days after discontinuing administration of gemfibrozil and simvastatin, the patient's condition improved and she was discharged home. Although this is the first report to indicate an association between myopathy and concomitant use of simvastatin and gemfibrozil, we strongly recommend caution and careful monitoring if simvastatin is given to patients receiving gemfibrozil.