Restenosis following percutaneous transluminal coronary angioplasty (PTCA) remains a serious problem in interventional cardiology. Recent trials using stent implantation have proposed a reduction in restenosis, presumably due to a higher initial luminal gain. This study was conducted to evaluate if the short- and long-term results following conventional PTCA may be favorable, if balloon dilation was performed according to measurements gained by intravascular ultrasound (IVUS) (vessel size adapted PTCA). The use of intracoronary stents might be omitted if comparable long-term results could be achieved by this modified technique of balloon angioplasty. This unicenter and nonrandomized pilot trial was initiated in January 1995 with 252 patients who had 271 lesions. IVUS was performed before and after intervention to determine the external elastic membrane (EEM) diameter at the lesion site. The balloon catheter was sized according to the EEM diameter measured by IVUS (EEM 10%). The mean balloon diameter was 4.1 +/- 0.5 mm, the dilation time 130 +/- 60 seconds with a balloon pressure of 7.0 +/- 2.0 atm. Clinical acute and 1-year long-term follow-up were obtained for all patients and follow-up angiography in 71% of patients. Acute events occurred postinterventionally in 5 patients (2%). The cumulative event rate during long-term follow-up was 14%. The angiographic restenosis rate (diameter stenosis >50%) after 1 year was 19%. Vessel size adapted PTCA using IVUS led to favorable acute and long-term results with a low restenosis rate and a low 1-year clinical event rate. Despite dissections that occur frequently using large balloon sizes, an increased rate of major complications did not occur, indicating a safe procedure and substantiating the philosophy of "therapeutic dissections." The results need to be verified in a randomized trial.