Following implantation of coronary Palmaz-Schatz stents, 29 patients were anticoagulated with a combination of heparin, phenprocoumon and aspirin following a standard protocol. After removing the arterial and venous lines, post-interventional intravenous (i.v.) heparin treatment started with 1500 IU/h for patients > 80 kg and 1250 IU/h for patients < 80 kg. Heparin was monitored by the activated partial thromboplastin time (aPTT) and adjusted by increasing or reducing i.v. heparin by 250 IU/h to maintain the aPTT within the therapeutic range. Phenprocoumon therapy began the day after stent implantation (day 2) and lasted for 3 months. aPTT, Heptest, prothrombin fragment F1 and 2 (F1.2) and thrombin-antithrombin III complexes (TAT) were monitored at standard intervals for 10 days (mean monitoring time: 9.7 +/- 2.3 days). Anticoagulation was efficient with aPTT levels remaining within the therapeutic range on day 9 and the simultaneous, moderate-onset oral anticoagulation within the therapeutic range of the International Normalized Ratio (INR; 2.15-4.80) on day 8 on average, the mean INR being 2.43 +/- 0.76. On day 4, F1.2 levels were significantly higher than on the day of stenting (1.16 +/- 0.30 nmol/l vs 1.04 +/- 0.53 nmol/l; P < 0.005). F1.2 levels fell after day 5, the difference becoming significant from day 8 on (P < 0.05). F1.2 was negatively correlated with the Heptest (P < 0.05) and fell significantly as a function of the INR during phenprocoumon administration (P < 0.001). After phenprocoumon therapy was discontinued over 3 weeks, 25 patients were followed up by angiography. Despite adequate anticoagulation, mean F1.2 levels in patients showing restenosis at follow-up angiography were significantly higher (P < 0.005) than in those without restenosis. In one patient who developed subacute stent thrombosis, clotting factors were determined 20 min before stent occlusion. The levels of F1.2 and TAT were less than all other patients on this day (F1.2: 0.98 nmol/l vs 1.11 +/- 0.40 nmol/l; TAT: 2.7 micrograms/l vs 3.21 +/- 3.38 micrograms/l). Thus, neither F1.2 nor TAT predicted the occurrence of thrombotic stent failure in individuals. Efficient anticoagulation by a combination of anticoagulants is imperative for stent implantation. Using only current routine methods, this way of monitoring anticoagulation is effective for managing combined anticoagulation therapy.