The inner one-third (IM) of both lateral and medial menisci resembles hyaline cartilage, both in gross appearance and histological examination, while the outer two-thirds (OM) is fibrocartilaginous in appearance. Collagen was extracted with pepsin, purified with anion and cation exchange column chromatographies and examined by differential salt precipitation, cyanogen bromide-peptide analysis and SDS gel electrophoresis. IM constitutes approximately 10% of the wet weight of whole meniscus, is made up of 70% collagen of which 34% is pepsin soluble. IM is composed of 60% type II and 40% type I collagen. OM is made up of 80% collagen of which 17% is pepsin soluble. The predominant collagen of OM is type I with a trace amount of types III and V (less than 1%).