Carcinoma metastatic to the ureter is uncommon, only 160 patients having been reported upon to date. During a ten year period, 82 patients with ureteral obstruction, secondary to metastatic disease, were seen at the UCLA Hospital. A critical analysis of the records of these patients revealed important clinical and diagnostic criteria to aid in the evaluation and treatment of extrinsic ureteral obstruction. Tumors of the cervix, prostate, breast and colon-rectum were the most common primary lesions to metastasize to the ureter. Subtle changes in urinary symptoms or in laboratory values should alert the physician to the possibility of ureteral involvement. Early detection of metastatic ureteral obstruction prior to the ravages of uremia may allow time for more aggressive use of adjuvant therapeutic modalities that would, at a later stage of the disease, be ineffectual or contraindicated.