The authors report 5 cases of embryonic sarcoma of the uro-genital sinus. 3 children, aged respectively, 17 months, 2 1/2 years, 6 years and two adolescents of 17 and 19 years. There were 3 boys and 2 girls. In only one case was the tumour obvious on clinical examination. In all the other cases, it caused urinary retention. On cystography, there was a polycyclic vesical filling defect resembling a parachute, which is specific of the botryoid variety and always leads to the right diagnosis. In girls, sarcoma of the urogenital sinus above the bladder, may be confused with other pelvic tumours. The authors recall the importance of lateral views of cystography to eliminate, if necessary, low paravertebral neurogenic tumours or sacro-coccygeal dysembryomas. After discussing the pathology, and the clinical and radiological findings, the authors then review rapidly the present methods of treatment which give a large number of survivals and should lead one to treat all cases, even when there are recurrences or metastases.