OBJECTIVE: A new balloon protection catheter to prevent distal emboli during internal carotid artery percutaneous transluminal angioplasty and stenting was developed, and its efficacy was evaluated in both an experimental model and clinical cases. METHODS: The balloon protection catheter was navigated over a steerable 0.014-inch guidewire to negotiate tight stenoses and sharp bends, which would cause difficulties for the passage of a flow-directed balloon catheter. Percutaneous transluminal angioplasty and stenting were performed for 85 consecutive patients with 87 stenotic lesions of the cervical internal carotid artery, with two different methods using this protection system. Distal protection was provided only after dilation for the initial 38 lesions (Group I), but the latter 49 lesions were treated in both the pre- and postdilation periods (Group II). The effects of using the balloon protection catheter with the embolic debris clearance technique were evaluated with pre- and postoperative magnetic resonance imaging for each group. RESULTS: The balloon protection catheter was introduced beyond the stenosis in all cases. In Group I, one symptomatic embolic stroke was caused by distal embolization resulting from atheromatous plaque, and high-intensity areas appeared on diffusion-weighted magnetic resonance imaging scans in 47% of cases. In contrast, in Group II, there were no strokes related to the procedure, although one patient with multiple risk factors died suddenly on the second day after stenting. Diffusion-weighted imaging scans demonstrated small, high-intensity areas in 19% of cases in Group II. The overall morbidity/mortality rate in our series was 2.3%. CONCLUSION: Our new balloon protection catheter was reliably navigated across internal carotid artery stenoses and reduced distal embolism in clinical cases.