The clinico-pathological features and surgical management of 19 unduplicated ectopic ureters in 15 children are presented with special reference to the problems of recognition and treatment and to the underlying embryological and pathological significance of the wide-ranging associated abnormalities. The high incidence of renal and ureteric malformations, both ipsilateral and contralateral, is emphasised, as is also the frequent co-existence of vesical, bladder neck, urethral, genital and anal abnormalities. These associated anomalies modify the presentation of unduplicated ureteric ectopia and may mask its presence. Late recognition is common, but may be avoided by awareness of the problem. Whereas the degree of kidney involvement seems to dictate the choice and priorities of surgical treatment, the lower urinary tract anomalies have more significance as regards continuing disability and these largely determine the outcome in relation to continence.