Twenty patients with previous unilateral traumatic hyphaema and 25 age-matched controls were studied. There was a progressive rise in intraocular pressure when the patient changed from the standing to the sitting position and then to the lying position in both groups. No control eye showed a rise greater than 2 mmHg when the subject changed from sitting to lying. However, 14 (70%) of the injured eyes and 12 (60%) of the fellow eyes showed an exaggerated response. We suggest that the presence of an abnormal postural response may indicate a predisposition to post-traumatic glaucoma. Our findings are compatible with a linked control of postural intraocular pressure response between the two eyes.