The authors report the 22nd case of double ureter to be published in the literature, in which one ureteral branch had a blind ending and did not terminate in any parenchyma. The condition was discovered during on antireflux operation for reflux in the lower pelvis of one Kidney which was known to be duplicated, and reflux in an apparently single contralateral pelvis. The pathological implications of this blind ureter are not well defined. The embryogenesis of the ureter and of ureteral duplications is reviewed and a general classification of double, bifid, and blind ureters outlined. Double ureter with one blind branch are three times more frequent in women than in men and are associated in 30 per cent of cases with contralateral bifid or duplicated ureters. The published literature is reviewed in detail.