Urodynamic investigations were performed in 9 males, suffering from dysfunction of the bladder neck (detrusor bladder neck dyssynergia). The parameters of micturition were compared with the values in normal males and in patients with prostatic obstruction. By introducing a new factor, the maximum opening time, we found a characteristic pattern in dysfunction of the bladder neck, making selection of patients for endoscopic incision of the bladder neck possible. The maximum and mean flow rates increased significantly in 5 patients treated with incision of the bladder neck. The diagnostic value of voiding cystourethrography and urodynamic investigation is discussed.