Ultrastructural studies were carried out on intercellular relationships during osteocyte differentiation in primary parallel-fibred bone of newborn rabbit. It was found that throughout the whole differentiative process preosteocytes are in close relationship with the neighboring cells (osteoblasts, osteocytes) by means of variously-shaped intercellular contacts (invaginated finger-like, side-to-side, and end-to-end) and two types of specialized junctions: gap and adherens. The pivotal role played by these contacts and junctions in osteocyte differentiation and activity is considered in the context of their particular functional significance.