Reexamination of the micturition cystourethrograms in 289 adult male patients with subvesical obstruction proved that the cause of the narrowing can be accurately diagnosed on the pattern of the urethral lumen. The radiologic and the final urologic diagnoses coincided in 87.5 per cent of all cases. The narrowing localized to the bladder outlet associated with short supracollicular urethra correlated well with the urologic diagnosis of bladder neck contracture. In this group 37.9 per cent of the cases presented evidence for an inflammatory etiology. 19 per cent of the same group had patterns which resembled very much nodular hyperplasia. Other possible etiologies for the bladder neck contracture did not appear to produce characteristic patterns.