The characteristics of the bone matrices formed by osteogenic cells isolated from both chick embryonic calvaria and hen medullary bones were examined. Isolated calvarial cells had developed organelles in the cytoplasm compared to isolated medullary bone cells. The cells isolated from both types of bones exhibited alkaline phosphatase (ALP) activity. Isolated calvarial cells formed a matrix that contained small amounts of acid mucopolysaccharide and densely-distributed thick collagen fibers. On the other hand, isolated medullary bone cells formed a matrix that contained a large amount of acid mucopolysaccharide and sparsely-distributed thin collagen fibers. Both matrices displayed calcium deposits. These results suggest that cells isolated from embryonic chick calvaria and hen medullary bones have the capacity for osteogenesis, forming cortical bone-like matrix and medullary bone-like matrix, respectively.