38 cases of severe hypertension due to a vascular abnormality of the renal pedicle were studied in children under 16 years of age, 18 boys and 20 girls. The most common presentation was at routine clinical examination. The diagnosis of an abnormality of the renal artery was suggested by the appearances of intravenous urography. There were many causes; 4 aneurysms of the renal artery or its branches, 4 fibromuscular dysplasias with one case of bilateral fibromuscular dysplasia, 4 idiopathic stenoses, 2 endarteritis, and 6 thromboses revascularised to variable degrees (2 after umbilical vein catheterisation and one due to DLE). In three cases the hypertension was related to compression of the pedicle by a tumour of haematome, and 14 cases had multiple arterial lesion. In the latter group, 6 cases of neurofibromatosis, 2 cases of William and Beuren's disease, 1 case of generalised Elastorhexia, 2 cases of aortic medio stenosis, probably Takayashu's disease, and 3 unidentified conditions. Surgery was performed on 29 patients, 21 of whom had unilateral lesions and were definitively cured of hypertension. Of the 8 cases with multiple lesions, only 2 were completely corrected with cure of their hypertension.