Apparatus and methods are provided for treating lesions within a blood vessel include a two-layer angioplasty balloon designed for the simultaneous deployment of multiple balloon-expanded stents. The high-compliance (elastic) outer balloon secures stent position. The low-compliance (inelastic) inner balloon drives angioplasty and stent expansion. Stent deployment starts with the injection of a small quantity of fluid into the outer balloon, which bulges slightly at both ends and into the spaces between the stents and, once the stent has expanded a little, between the struts of the stents. The injection port to the outer balloon is then closed, and fluid is injected only into the inner balloon, which expands, opening the stents.