This paper presents our initial experience with a new low-profile balloon "on-a-wire" catheter, the Bijou. The concept of this balloon is to provide an additional side lumen with the advantages of (1) the ability to measure pressure gradient, (2) the possibility of drug infusion, and (3) the ability to advance a steerable guidewire through this side lumen. The balloon has been tested in 15 patients; 14 underwent an elective procedure for stable angina pectoris (with 2 cases of restenosis) and one an emergency angioplasty in a case of acute myocardial infarction. The stenosis was located on the left anterior descending artery in 11 procedures, on the right in 3, on a marginal branch in 2, on the circumflex and a saphenous vein graft in 1. All stenoses could be dilated successfully (residual stenosis < 25%). The transstenotic pressure gradient felt from 49 +/- 13 mmHg to 7 +/- 4 mm Hg after angioplasty. Except for an uncomplicated dissection in 3 patients, no other complication was noted. With this new catheter, the double-lumen configuration adds the advantages of an "over-the-wire" to an "on-a-wire" system.