The immediate changes in stenosis geometry following Wallstent and Wiktor stent implantation in native coronary arteries were compared in 92 patients (46 in each group) using automated edge detection. Patients with comparable baseline stenosis characteristics were selected. Lesions were matched for lesion site, reference diameter, and minimal luminal diameter. In both groups, the stented coronary artery was the left anterior descending artery in 27 patients (59%), the left circumflex artery in four patients (9%), and the right coronary artery in 15 patients (33%). The baseline reference diameter was 2.86 +/- 0.39 mm and 2.87 +/- 0.42 mm in the Wallstent and Wiktor stent study group, respectively (NS). The baseline minimal luminal diameter was identical in both groups (1.13 +/- 0.24 mm). The nominal size (mean +/- SD) of the unconstrained Wallstent was 3.5 +/- 0.3 mm and 3.3 +/- 0.3 mm for the Wiktor stent (P less than 0.05). Both types of stents resulted in a similar increase in minimal luminal diameter immediately following implantation (Wallstent: 2.34 +/- 0.38 mm, Wiktor stent: 2.43 +/- 0.27 mm, NS). Furthermore, there was a similar decrease in diameter stenosis and increase in minimal luminal cross-section area following implantation of both stents. These morphological changes were associated with a normalization of the hemodynamic parameters in both groups. It is concluded that, although the Wallstent and Wiktor stent are different in design and mechanical characteristics, there is a similar immediate improvement in stenosis geometry following implantation of both devices.