From January 1988 to December 1991, 343 women were operated for genital carcinoma at the 1st Gynaecological Department of the University Munich. Additionally to the corresponding cancer operations, pelvic or pelvic and paraaortic lymphadenectomy was performed. In a postoperative systematic and prospective study with ultrasound, we detected a high incidence of 48% of postoperative lymphocysts. Only a few were symptomatic and even less required therapy. In this study we were especially interested in the influence of closure of the pelvic peritoneum on the incidence of lymphocysts. Thus, we inaugurated a prospective study in 1991 with 49 patients with an open peritoneum and compared these results to 294 women who had standard closure of the peritoneum. There was a significantly higher rate of lymphocysts in patients with peritoneal closure (45.2%) in comparison to 20.4% lymphocysts in patients without peritoneal closure. In the study group (open peritoneum) 6.1% of the patients with lymphocysts showed symptoms, only 4.1% needed therapy. In the control group (closed peritoneum), 14.6% of the patients with lymphocysts were symptomatic and 8.2% needed therapy. These differences are not statistically significant. Other complications such as haemorrhage, fever or ileus were comparable in both groups. Our results do not supply sufficient proof, that leaving the peritoneum open significantly reduces symptomatic lymphocysts.