Apparatus and method are provided for treatment of a bifurcation of a body lumen. The apparatus includes an elongated catheter body having a proximal end and a distal end. A balloon is associated with the distal end of the balloon catheter. The balloon includes a main vessel balloon for treating a main vessel of the bifurcation, and a branch vessel balloon for treating a branch vessel of the bifurcation. The branch vessel balloon includes an accordion configuration capable of being expanded from an unexpanded collapsed accordion configuration to an expanded accordion configuration extending into the branch vessel.