Background. Since the report that hypertension associated with Wilms tumor (WT) may be renin-induced, no larger series than 13 patients have been published. Nevertheless, angiotensin converting enzyme (ACE) inhibitors have become treatment of choice for hypertension in WT patients. The purpose of this study was to investigate the correlation between plasma renin levels and blood pressure in a larger cohort of WT patients. Procedure. In this retrospective, single-center study, data on blood pressure and plasma renin were analyzed in 86 WT patients treated according to the consecutive SIOP protocols 6, 9, 93-01, and 2001. Results. At diagnosis, 47 WT patients suffered from hypertension (55%). In 31 of these patients plasma renin levels were analyzed; increased plasma renin levels were found in 25/31 patients (81%). In contrast, normal plasma renin levels were measured in 8/13 of the patients with a normal blood pressure (P = 0.012). Twenty-eight children received antihypertensive treatment before surgery, in 25 of them blood pressure normalized before surgery. Blood pressure was normal directly after surgery in all patients but 4, in whom blood pressure recovered to normal within a few weeks. Conclusions. This retrospective study shows that hypertension in WT patients is associated with elevated plasma renin levels, indicating that ACE inhibitors may be a good therapeutic option in at least a subset of WT patients with hypertension before nephrectomy.