Energy metabolism of perfused rabbit ear chondrocytes was studied by using 31P-nuclear magnetic resonance (31P-NMR) and high performance liquid chromatography (HPLC). Rabbit ear chondrocytes contained a relatively low concentration of creatine phosphate and high concentrations of GTP and UTP, compared with that of ATP. Concentrations of high-energy phosphate compounds and pH in the chondrocytes did not change when the oxygen concentrations of the perfusate were 95, 20 and 7%. However, high-energy phosphate compounds decreased when the perfusate did not contain oxygen, and when it contained 1.0 mM KCN or 0.1 mM dinitrophenol. A decrease in pH due to accumulation of lactate was observed simultaneously. The findings suggested that a large part of high-energy phosphate compounds in rabbit ear chondrocytes are consumed in the process of matrix production. Oxygen supply was necessary in order to maintain intracellular concentrations of these high-energy phosphate compounds.