An increased fibrin level enhances the activity of proangiogenic factors and may contribute to tumor formation. Formation of new blood vessels during angiogenesis leads to neoplasm development through interaction with factors such as basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF) and interleukins. The aim of this study was to investigate the influence of perioperative antibiotic therapy in women with benign gynecological tumors with regard to basic fibroblast growth factor level, fibrinogen concentration and fibrin viscosity. The influence of clindamycin plus metronidazole therapy (group I) and cephazolin therapy (group II) on fibrinogen concentration, level of bFGF and fibrin viscosity was studied in women diagnosed with nonmalignant myomas and cysts. In patients with benign gynecologic tumors, higher bFGF levels (51.40 +/- 13.72 pg/ml), fibrinogen concentration (348.26 +/- 164.74 mg/dl) and fibrin viscosity (2.63 +/- 0.36 mPa) were observed, as compared with healthy women. There were strong indications that antiangiogenic activity occurred with both clindamycin plus metronidazole and cephazolin, although the response to these particular antibiotic therapies was different. The use of various drug therapies in groups I and II resulted in faster and delayed antiangiogenic effects, respectively. Further research is essential to provide more detailed information about the mechanisms of the induction of antiangiogenic activity by perioperative adjuvant antibiotic treatment.