Four new cases of spontaneous extravasation of contrast medium during intravenous urography have been described. All were due to non-acute obstruction of the ureter. This is relatively uncommon as most of the cases previously described have been due to passage of a ureteric calculus. Two of the patients improved after relief of the obstruction. In one a nephrectomy was carried out, and one patient died of an unrelated cause before the obstruction could be relieved.