Radioautographic procedures were used to examine the incorporation of 3H-fucose into macromolecular material in bone organ cultures. Radioautography demonstrated that silver grains were first apparent in the paranuclear area of osteoclasts, and continued to increase in number over osteoclasts throughout the culture period. Silver grains associated with osteoclasts were later found on the side adjacent to bone and the adjacent bone surface. Osteoblasts, pre-osteoblasts and fibroblasts of the fibrous periosteum incorporated some 3H-fucose as evidenced by labelling in the later time periods. At later incubation periods, labelled material was found in the underlying bone below osteoblasts, demonstrating the active elaboration of bone matrix glycoproteins. Osteocytes were labelled only after the longest period of incubation.