1. The utilisation of labelled proline in normal and injured mature rabbit articular cartilage has been studied and compared simultaneously in one phase of the study with radiosulphate utilisation. The morphologic features of lacerative injury paralleled those reported previously.

2. Labelled proline is actively utilised by mature articular cartilage and can be recovered in time from the matrix as labelled hydroxyproline. This is taken as evidence of collagen synthesis.

3. Evidence is presented to suggest that the rate of formation of labelled hydroxyproline may be augmented after lacerative trauma.

4. Parallel utilisation of radiosulphate and labelled proline suggests that the synthesis of chondromucoprotein and collagen are closely related and that the continual synthesis of both moieties is necessary for the maintenance of normal matrix.

5. Despite evidence of increased chondromucoprotein and collagen synthesis no significant contribution is made to the healing of lacerative defects in mature rabbit articular cartilage.