The use of hydrostatic pressure to apply mechanical stress to bone organ cultures is reviewed. Ossifying long bones and calvarial rudiments are sensitive to this type of stress. Intermittent hydrostatic compression of near physiologic magnitude (ICF) has anabolic effects on mineral metabolism in such rudiments, and continuous hydrostatic stress of high magnitude (CCP) has catabolic effects. The effects of ICF may be ascribed to shear stress generated at tissue interphases of different chemical and mechanical properties. Local factors, such as prostaglandins and growth factors, seem to be involved in the tissue response to mechanical stress.