Background: Recently, T-stenting with Cypher stent was not proved to be effective in bifurcation lesion, mainly because of poor stent ostial coverage of side branch. Still provisional approach seemed to be reasonable for two-stent technique has never been proved to be better than one-stent technique. This study was to evaluate the efficacy of provisional T-stenting with secure ostial coverage of side branch. Methods: This study was designed as single center prospective registry. Patients with a bifurcation lesion stentable with ���2.5 mm stent for both branches were enrolled. Exclusion criteria were cardiogenic shock, ST elevation myocardial infarction within 1 week, thrombotic lesion, and instent restenosis. Side branch stenting was implanted when residual stenosis ���50% or dissection. Procedure was performed with standard technique of provisional T-stenting except the ostium of side branch was securely covered with a stent by intentional small protrusion into parent vessel. all procedures were performed with Cypher stent with intravascular ultrasound guidance. Results: One-hundred two lesions in 101 patients were included. Left anterior descending artery lesion comprised 54%, and left main 35%. True bifurcation was noted in 53%. The procedural success rate was 100%. Out of 102 lesions, side branch stent was implanted in 62 lesions (61%). After the procedure, the peak CK-MB level more than 3 times of upper normal limit was noted in 19% of the cases. Thirty-day clinical follow-up was completed in all patients. One patient died from subacute thrombosis. Otherwise no event was noted. Out of 49 patients who complete 9-months clinical follow-up, there was no death and no myocardial infarction, but 4 target vessel revascularizations were noted (8.1%). All events were noted in 2-stent group. In 42 patients who completed 9-month angiographic follow-up, restenosis was noted in 3 patients, 2 for parent vessel, 1 for side branch. Late loss was 0.45짹0.65 mm for parent vessel, and 0.26짹0.60 mm for side branch. Last patient follow-up is expected to be the end of this year. Conclusion: Provisional T-stenting with secure ostial coverage of side branch seems to be the most reasonable approach for all bifurcation lesions.