Complete occlusion of the renal vein in five rabbits with the kidney in its normal position was followed by high-resolution ultrasound. Early changes consisted of moderate renal enlargement and a diffuse increase in renal echogenicity with a fine echo pattern. On the average, renal length increased by only 13%. Delayed changes were a gradual reduction in renal echogenicity, falling to below baseline, with blurring of the corticomedullary boundary. Intrarenal hemorrhage alone occurred in only one kidney. Perirenal hematoma were seen in two other cases associated with localized intrarenal hemorrhage adjacent to the point of capsular rupture (overall renal morphology was preserved). The relative subtlety of the changes observed contrasts with previously reported data and is felt to preclude a specific diagnosis.