Background: We evaluated the effects of daflon, a venomimetic agent that regulates the circulatory tonus of the venous system, on pelvic pain and investigated the role of enlarged veins in the pathophysiology of pelvic congestion syndrome. Methods: Twenty women (age 28-35 yrs) with chronic pelvic pain were diagnosed with the syndrome at laparoscopy. They all had prominent broad ligaments and ovarian veins without other pathologies such as endometriosis to explain the etiology of pelvic pain. Ten women were randomized in a fashion to receive 500 mg of Daflon twice/daily for six months, and ten a vitamin pill for placebo effect; they were crossed over for another six months. Results: At the end of the third month, the frequency and severity of pelvic symptoms began to decrease with daflon compared with the pretreatment and vitamin arm. The mean scores were significantly less at the end of six months, respectively, p<0.05. Conclusions: Pharmacologic enhancement of venous tonus may restore pelvic circulation and relieve pelvic symptomatology.