High flow infravesical obstruction in male patients with severe prostatism is defined by a maximum flow rate of more than 15 ml. per second and a vesical pressure exceeding 100 cm. water at maximum flow rate. During a 9-month period urodynamic screening of 225 patients referred to our hospital with prostatism revealed high flow infravesical obstruction in 16 (7 per cent). Transurethral surgery of the prostate or bladder neck was performed in 11 of the patients, with good results observed in symptomatology as well as in maximum flow rate. A urodynamic screening program is suggested to establish the diagnosis so that these patients can benefit from surgical treatment.