Bone wax is the substance which has been used for hemostasis in different surgical fields for up to one hundred years and historically used in our center to prevent sternal bleeding and subsequent complications. Recently, reabsorbable gelatin powder has come into use. Up to now there are no clinical studies that compare these two substances. Between 1st January and 31st December 2004, 1249 subsequent patients have been operated on for different cardiac surgical procedures in our center, of them 557 were enrolled in a randomized perspective monocentric study. They have been divided into two similar subgroups: one treated with swine gelatin plus rifamycin (group one) and the other with bone wax (group two). The two hemostatic products have been applied just after the sternotomy and before the chest closing. Each patient was evaluated for bleeding, sternal infections and was followed-up for two months for bone and wound healing. Postoperative bleeding at the tenth hour was 315 ml+/-269 (mean+/-S.D.) in the first group and 395 ml+/-265 in the second (P<0.001). In the 10th-20th hour interval time bleeding was 120 ml+/-74 and 205 ml+/-132, respectively (P<0.001). Total bleeding was 415 ml+/-87 in group one and 580 ml+/-150 in group two (P<0.001). Chest reopening for bleeding not due to surgical problems was carried out in 14 patients (4.7%) (group one) and 19 (7.3%) (group two) (n.s.). Superficial sternal wound infection occurred in two patients (0.7%) in group one and three patients (1.1%) in group two (n.s.). There were no deep sternal wound infections. Bleeding was significantly higher in patients treated with bone wax compared to those with absorbable gelatin plus rifamycin.