An investigation on the therapeutic effect of L-carnitine was performed at three different centres and included two hundred patients, 40 to 65 years of age, with exercise-induced stable angina. In one hundred randomly selected patients the drug was administered orally in daily doses of 2 g in addition to the already instituted therapy, and the effect studied over a 6-month period. Compared with the control group, these patients showed a significant reduction in the number of premature ventricular contractions (PVC) at rest, as well as an increased tolerance during ergometric cycle exercise as demonstrated by an increased maximal cardiac frequency, increased maximal systolic arterial blood pressure and therefore also increased double cardiac product and reduced ST-segment depression during maximal effort. This was accompanied by improvement in cardiac function and resultant performance, as shown by an increase in the number of patients belonging to class I of the NYHA classification and a reduction in the consumption of cardioactive drugs. Laboratory analysis showed an improvement in plasma lipid levels. The authors conclude, after having discussed the particular metabolic mechanisms, that L-carnitine undoubtedly represents an interesting therapeutic drug for patients with exercise-induced stable angina.