Eleven cases of hypertension after renal trauma were reviewed. The average age of the patients was 22 years on first examination at the Cleveland Clinic. Ten patients were asymptomatic; 4 were not aware that they had suffered specific renal trauma. The onset of hypertension occurred at very different intervals after the traumatic event, sometimes after several years, thus making imperative long-term observation of patients suspected of having sustained renal trauma. Nephrectomy ameliorated hypertension in 7 of 8 patients, 6 of whom became normotensive; more conservative operations failed to relieve hypertension in 2 of 3 patients. Mechanisms of post-traumatic renal hypertension include parenchymal compression from hematomas (analogous to the cellophane-wrapped kidney of Page) and renal artery stenosis or occlusion (analogous to the Goldblatt kidney).