Contradictory data concerning the use of non-ionic contrast media during percutaneous coronary angioplasty (PTCA) have been published. Many clinical studies have suggested that a higher rate of PTCA complications (using balloon angioplasty) was observed using non-ionic versus ionic contrast media. In order to verify these results in the era of coronary stenting, we compared the in-hospital outcome of 384 patients (pts) dilated using ionic contrast media (ioxaglate) and 387 pts dilated with non ionic contrast media (iopamidol). From October 15th 1993 to July 15th 1994, 773 consecutive pts were included in this study. At the beginning of the procedure, the pts received a first bolus of heparin (7500 IU for pts who had not been pretreated with heparin and 5000 IU for pts already treated with heparin). After the first bolus the activated clotting time (ACT) was measured and the pts received an additional bolus of 2500 IU when the ACT was below 300 sec. When the procedure exceeded one hour an additional bolus of 5000 IU was injected. The main characteristics of the 2 groups (Ioxaglate vs Iopamidol) were comparable (demographic data, indication of PTCA, procedural data, first dose of heparin, total dose of heparin). The final ACT was higher in the ioxaglate group (634 +/- 111 vs. 474 +/- 310, p < 0.001). During the hospital course, blood transfusion or vascular surgery was necessary in 1.6 vs. 1.0% (NS), acute closure occurred in 2.1 vs. 4.9% (p = 0.03), acute Q-wave myocardial infarction in 0.5 vs. 0.75% (p = NS), emergency bypass surgery in 0 vs. 0.5% (NS), death in 0.8 vs. 0.3% (NS) and major cardiac event (death, myocardial infarction, coronary artery bypass surgery) in 0.8 vs. 1.6% (NS). Stents were less frequently used in the Ioxaglate group (21.5 vs. 28.5%, p = 0.03) especially in the subset of bailout stenting (2.0 vs. 4.9%, p = 0.04). CONCLUSION: This study suggests that PTCA with provisional stenting can be performed safely using ionic or non-ionic contrast media. However, the ACT obtained with the same dosage of heparin is significantly higher with the ionic contrast media whereas the risk of acute closure and the rate of bail-out coronary stenting is lower.