Multicystic renal dysplasia is an extremely uncommon cause of hypertension in children and the few reported cases have not been of newborns. We report on a neonate in whom severe hypertension associated with elevated peripheral plasma renin resulted from a unilateral multicystic dysplastic kidney. Hypertension and plasma renin activity normalized after unilateral nephrectomy. No evidence of perfusion or excretory renal function in the dysplastic kidney was present on a radionuclide renal scan. This child demonstrates a relationship between hypertension and unilateral multicystic renal dysplasia.