Introduction: Between September and December 2012, unusual postoperative bleedings occurred in all on-pump cardiac surgery in our heart-surgery department of Clermont- Ferrand University Hospital. This issue was concomitant to the replacement of Choay heparina by Panpharma heparin. The aim of this study is to compare the postoperative hemostasis between these two heparins. Material and methods: We retrospectively compared the operative and postoperative surgical data from patients who had undergone surgery during this 4-month period when Panpharma heparin (group P, 257 patients) was used with data from patients who had undergone surgery during the following 3 months and received Choay (group C, 194 patients). Results: There was no significant difference between the two groups in terms of preoperative characteristics, operative indications, or theoretical heparin doses. Despite group P receiving a significantly lower total dose of heparin (mean dose 21 000 IU/CEC) compared to group C (mean dose 22 000 IU/CEC) ( P = 0.05), the number of surgical re-explorations needed to perfect postoperative hemostasis was significantly higher for group P (3.5% vs. 0) (P = 0.01). Heparin anti-Xa activity after surgery had higher anticoagulant activity in group P at postoperative h1 and h12 compared to group C, which accounted for the greater postoperative surgical re-explorations in group P