We investigated the effects of increased intraosseous pressure on new-bone formation in the proximal metaphysis of the caprine tibia. Intraosseous hypertension was produced by obstruction of venous outflow by ligation of the popliteal vein draining the proximal aspect of the tibia and occlusion of the medullary space with bone cement (groups 1 and 2). After the obstruction of venous outflow (day 0), the intraosseous pressure measured at the proximal tibial metaphysis increased significantly from a mean of 15.5 millimeters of mercury before the obstruction to a mean of 28.7 millimeters of mercury in groups 1 and 2. In group 1, obstruction of venous outflow was combined with intraosseous infusion of autogenous whole blood under pressure to maintain the intraosseous pressure between thirty and forty-five millimeters of mercury during days 0 through 5. The time for venous drainage was still prolonged and intraosseous pressures were still increased on days 5 and 10 (means, 26.8 and 26.2 millimeters of mercury, respectively) in groups 1 and 2. The intraosseous hypertension produced in group 1 was associated with a significant increase in periosteal (138 per cent), endocortical (369 per cent), and cancellous new-bone formation (889 per cent) at the tibial metaphysis compared with control values. Osseous necrosis within the metaphysis was not observed.