Terazosin was evaluated in 21 normotensive spinal cord injured patients with autonomic dysreflexia. The patients were followed for 3 months during which the autonomic dysreflexia severity and frequency were evaluated. Autonomic dysreflexia severity mean score was significantly improved when measured at baseline and at 1 week, 1 month and 3 months (10.3 +/- 4.2, 5.08 +/- 2.3, 3.83 +/- 2.5 and 4.5 +/- 1.4, respectively, p < 0.0005). No statistically significant change was seen in erectile function and blood pressure. Three patients complained of fatigue, 1 of whom had the dosage reduced from 5 to 2.5 mg. daily. Terazosin appears to be effective in preventing serious harm from autonomic dysreflexia without erectile function impairment. The effectiveness is significant in the first week and remains for at least 3 months.