The authors report two observations of monstrous ectasia of the prostatic urethra, in boys age 12, without any previous pathological history; discovered on at the time of major dysuria previous urinary troubles with chronic retention of 500 cl and 1.250 l respectively. In the absence of any organic obstacle, etiology relieves functional troubles. If functional explorations show a normal or hypertensive detrusor, then they discuss the possibility of vesico-sphincter dyssynergia or an obvious hypertension of the striated sphincter. From this moment onwards, purely intrinsic urethral functional trouble is plausible, all the more because the recovery was assured by treatments directed only at the urinary canal. In the first case, after surgical treatment owing to complex lesions (plastic reduction of the urethral ectasia preserving the posterior wall and respecting the striated sphincter) combined with diverticulectomies with urethral reimplantations), the patient recovered complete vesical waste removal at once, with normalisation of the flowmeter in six months. In the second case, a simpler treatment (sub-montanal urethrotomy of the principle) allowed a normalisation period of 10 months with complete vesical waste removal. The functional results are maintained after a period of nine and two years respectively. The integrity of the striated sphincter controlled post-operatively by the operatory gesture on the urinary canal and confronts the authors in the idea of intrinsic urethral pathology, although electronic microscopic examination may not have shown achalasia.