We aimed to determine the effects of simulated stent side-branch dilatation and subsequent redilatation of the central lumen. Following coronary stent implantation it may be necessary to dilate through the side of a stent to maintain branch patency. Branch dilatation through the side of 3.5-mm-diameter stents (AVE GFX, beStent, Crown, MultiLink, and NIR) was simulated in a plexiglass phantom using 2.5-, 3.0-, 3.5-, and 4.0-mm balloons. In further experiments, the main lumen was redilated with a 3.5-mm balloon after 3.0-mm side-branch dilatation. Thereafter, a 3.5-mm central and a 3.0-mm side-branch balloon were simultaneously inflated ("kissing balloons"). The larger the balloon size used for side-branch dilatation, the greater the distortion of the stent immediately distal to the side-branch, which for a 4.0-mm balloon ranged from 36% +/- 2% (Crown) to 65% +/- 6% (NIR). Central lumen redilatation or kissing balloons abolished this stenosis with little reduction of the side-lumen diameter. The main stent lumen compromise caused by side-branch dilatation can be abolished by main-lumen redilatation or by kissing balloons.