Proteoglycan metabolism of normal and histologically mild to moderate osteoarthritic cartilage explants were studied. Explants were obtained from the human knee of donors aged over 40 years. Proteoglycan content, synthesis and release were very similar in normal cartilage obtained from donors with focal osteoarthritis and cartilage obtained from donors without any sign of osteoarthritis. This suggests that cartilage obtained from donors with focal osteoarthritis indeed can be considered as "normal". The relatively large surface area-compared to their natural setting in the joint- of cartilage explants in culture did not affect the parameters measured, as there was a strong linear correlation between these parameters and the weight of the explants. From our results, we conclude that the use of full depth cartilage tissue explants is a reliable way to assess and compare proteoglycan content, synthesis and release in normal and osteoarthritic cartilage from the same donor.