Under the circumstances that appropriate first-choice guidewires for percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) have yet to be established, the objective of this study is to determine appropriate first-choice guidewires. G-FORCE study is a prospective multicenter randomized study between normal (distal tip size 0.014 inch) and slender (distal tip size 0.010 inch or less) guidewires. Primary end point is lesion penetration rate of the first choice guidewire.