Palmitic acid is a major physiological substrate of the myocardium and its role in myocardial metabolism is well understood. 11C labeled palmitic acid may be used with a positron emission tomograph (PET) to obtain high contrast images of transverse sections of the heart. A rapid and reliable method for producing [11C]palmitic acid from [11C]carbon dioxide by the Grignard synthesis is described. All interfering long chain nonradioactive impurities are removed by the purification procedure. As a result, this [11C]palmitic acid may be used as a tracer for pure palmitic acid in the measurement of regional myocardial function.