on in vitro incubation of articular and epiphysial cartilage of the ulna of the domestic pig 70 to 80 per cent of [U-¹⁴C] glucose was metabolised to ¹⁴C-lactate, but cartilage of the epiphysial plate produced up to five times as much ¹⁴C-CO₂ as articular cartilage, and the specific radioactivity of ¹⁴C (or ³⁵S)-chondroitin 4 (6)-sulphate isolated from epiphysial cartilage (following ³⁵S-sulphate incorporation) was about twice as high as that of articular cartilage. Six weeks after an osteotomy on both sides of the proximal epiphysial plate of the left ulna, the glucose uptake, lactate production, and the specific radioactivity of the glycosaminoglycans displayed no significant differences when compared with those of the corresponding epiphysial plate of the control right ulna, whereas a 50 per cent increase in the oxidation of ¹⁴C-glucose to ¹⁴c-co₂ was observed.