We report on the procedural outcome in 30 patients with acute coronary syndromes in whom stent implantation was attempted without predilatation. Elective stent implantation in infarct related coronary arteries after myocardial infarction might be superior to agioptasty alone. We retrospectively analyzed the result from 88 patients who had stent implantation for myocardial infarction or unstable angina. In 30 of these patients we attempted to implant a stem without predilating the vessel. Successful stent deployment was possible in 26 (87%). In four patients where it was not possible to cross the lesion, we could withdraw the stent to predilate the lesion. We did not attempt direct stent implantation if the lesion was calcified, long, involved major side branches or a tortuous proximal segment, or where the length of the lesion and diameter of the distal vessel could not be measured. A low profile, premounted stent was used. Procedural success was 100% in the group of 30 patients with direct stent implantation— not significantly different from the 93% success in the group of 58 patients whose lesions were predilated first but had more complex lesions. The incidence of complications did not differ significantly between the two groups and no instances of stent loss or displacement occurred in the direct implantation group. Stent implantation without predilatation is feasible and not associated with a higher incidence of complications, provided lesions that allow easy positioning of the stent are selected. It can shorten the procedure and duration of ischemic occlusion of the vessel, which would be of particular advantage in unstable patients or where a large area of myocardium is jeopardized.