In this intravascular ultrasound (IVUS) randomized trial we compared a strategy of direct stenting (DS) without predilation (n = 30) vs. conventional stenting with predilation (SWP) (n = 30) in patients with suitable type A or B non-calcified lesions in native vessels > or = 3 mm. Optimal deployment was achieved using angiographic criteria without interactive IVUS. The goal of our study was to determine whether stent expansion and coronary remodeling were similar. Maximal pressure inflation was comparable in the two groups (11.4 +/- 2.2 vs. 11.8 +/- 1.9 atm; NS). Stent deployment was obtained in all patients with complete apposition to the vessel wall. DS and SWP resulted in comparable lumen enlargement (5.4 +/- 2.5 vs. 5.5 +/- 2.1 mm2) with an identical mechanism: 66% of lumen enlargement was due to increased enlarged elastic membrane (EEM)-cross sectional area (CSA) (delta = 3.7 +/- 2.1 mm2 and delta = 2.4 +/- 6.8 mm2, respectively, p < 0.49) and 34% was due to a reduced P + M-CSA (delta = 0.02 +/- 6.9 mm2 and delta = 1.2 +/- 6.3 mm2, respectively, p < 0.50). We conclude that at the same maximal pressure inflation the mechanisms of stent expansion are similar in both DS and SWP groups. In this observational study, the IVUS data showed clearly under-expansion of stents in both groups in comparison with previously published CSA values (minimum stent CSA of 7.5 mm2).