A well-defined, longitudinal lesion in the avascular part of the medial meniscus of the right knee was made in 30 rabbits. After 3 months, the lesion was repaired surgically in 12 rabbits, was untreated in 12 rabbits, and a meniscectomy was performed in 6 rabbits. The articular cartilage was studied macroscopically and microscopically at 3-month intervals. Cartilage changes 3 months after meniscectomy were more pronounced than after meniscal repair or than in untreated lesions. However, meniscal repair did not reverse the cartilage changes.