We investigated the mechanism of hemospermia in patients with a midline cyst (MLC) of the prostate, focusing on cystic dilatation of the utricle (CDU) as a possible causative lesion. Of 138 patients with hemospermia 30 (22%) had an MLC, of whom 19 underwent transperineal needle aspiration of the MLC and bilateral seminal vesicles to determine the site of bleeding. Following MLC aspiration a mixture of dye and contrast medium was injected. The verumontanum was observed endoscopically and pelvic x-ray was done. Seminal vesicle fluid on 1 or 2 sides was hemorrhagic in 13 of the 19 patients (aspiration failed in 6) and fluid from the MLC was nonhemorrhagic in 5 of the 19 (aspiration failed in 7). The MLC communicated with the urethra (CDU) in 15 patients (79%) and with 1 or 2 ejaculatory ducts in 11 (58%). In 5 of 11 patients with communication with the ejaculatory duct hemospermia persisted for more than 1 year. Four of these patients were cured by transurethral unroofing of the CDU. CDU is a significant underlying lesion for hemospermia. Communication with the ejaculatory ducts was frequent in patients with chronic hemospermia and transurethral unroofing was effective for eliminating hemospermia.