To assess the long-term results of operation for adrenal hypertension and to evaluate reasons and potential risk factors for the persistence or recurrence of hypertension. Retrospective clinical study. Teaching hospital, Italy. 48 patients with benign adrenal tumours who were preoperatively hypertensive and treated by adrenalectomy between 1980 and 1996. Factors that influenced the persistence of hypertension after removal of the adrenal tumours. During a mean (SD) follow-up of 77 (12) months, 4 (8.3%) patients developed cardiovascular or cerebrovascular complications. 24 patients had had a history of hypertension for less than 5 years and the remaining 24 for 5 years or more. Blood pressure returned to the normal range after operation in 22 patients (46%). 14 patients (29%) had persistent hypertension that required treatment with antihypertensive drugs, but 12 required less intensive treatment than before adrenalectomy. Multivariate analysis showed that age at presentation was the only significant factor predictive of persistent hypertension (p < 0.05); sex, haematochemical tests, raised preoperative blood pressure, duration of hypertension preoperatively, and size of tumour were not. The success in reversing hypertension after adrenalectomy for benign tumour is strongly related to age at presentation.