Chondrocytes from the sterna of embryonal chicken were dissociated by enzymatic digestion. Dissociated cells were cultured within collagen gels for 8 days. The cells increased 3 fold in 8 days. The gels gradually became white cartilaginoid tissue in appearance. Morphologic study showed that cells lied in lacunae and maintained the differentiated characteristics of cartilage. Extracellular matrix produced by cells deposited on exogenous collagen. Biochemical analysis showed that the collagen newly synthesised by the cells was type II collagen. This experiment demonstrates that collagen gels provide a suitable environment for chondrocyte growth, proliferation and differentiation, and chondrocytes embedded within collagen gels reconstitute cartilaginoid tissue.