Bovine dental pulps were prepared in large quantities and respiration studies were made on homogenates and mitochondrial fractions. Succinate was the only Krebs cycle intermediate that elicited a respiratory response. The addition of ADP or NAD + had no effect on endogenous respiration, but these cofactors inhibited succinate respiration when they were added in high concentrations, and stimulated succinate respiration when they were added in low concentrations.