Carnitine concentration was measured in human tissue obtained at surgery or autopsy. In all patients, the concentration of carnitine (nMol. g-1 tissue) was higher in epididymis than in testis, vas deferens, prostate, and seminal vesicles. There was no correlation between the tissue levels of testosterone in the testis and the concentration of carnitine in epididymis. As in the rat and baboon, carnitine is also found in high concentrations in the human epididymis.