Femoral heads were resected from patients with Mseleni joint disease, and cartilage present in 'islands' on the articulating surfaces and over marginal osteophytes was removed for study. Some specimens were grown in short-term organ culture and labelled with sulphur-35. Proteoglycans present in the tissue, and newly synthesised macromolecules were extracted, purified and assessed. The results indicated that very few of the proteoglycans present or synthesised during culture were capable of aggregation with hyaluronate and that the average size of the macromolecules was smaller than normal. In addition a large proportion of the proteoglycans were very small in size and were thought to resemble a molecule found in immature articular cartilage. The response to degenerative disease was unusual and may be peculiar to the Mseleni condition.