The significance of Ca 2 + is assessed for the activation of pyruvate oxidation by intact nerve terminals (synaptosomes). Titration of glucose-depleted synaptosomes with pyruvate in the presence of either veratridine or uncoupler stimulates respiration in a Ca 2 + -independent manner. Additionally, the ability of exogenous pyruvate to support the mitochondrial membrane potential in situ is independent of Ca 2 + . It is concluded that Ca 2 + does not regulate pyruvate oxidation in intact synaptosomes.