The pyruvate dehydrogenase complex (PDC) from the rabbit adrenal mitochondria was partially purified (18-fold) and its main kinetic parameters were determined: Michaelis' constants for pyruvate, CoA and NAD are 16, 10 and 140, respectively. The inhibitor constant for acetyl-CoA is 25 μM. Phosphate ions augment the PDC affinity for the substrate. After ACTH administration to rabbits the active PDC form in the adrenals rises simultaneously with the PDC phosphatase activity growth. The data obtained are indicative of the adrenal PDC involvement in mobilizing metabolism to provide intensive steroidogenesis.