The aim of this study was to identify independent angiographic predictors of collateral channel (CC) tracking success, microcatheter tracking failure, and complications in chronic total occlusion (CTO) retrograde approach. We also developed a "crossability score," comparing its predictive performance with pre-existing scores. The retrograde approach was introduced for recanalization of challenging CTOs. The passage of guidewires through CCs is a key step of the procedure. Two scoring systems have been recently developed to predict CC tracking success. A total of 180 patients and 297 CCs were retrospectively analyzed in an unselected retrograde CTO population. Guidewire crossing was successful in 203 collaterals (68.3%). The only independent predictor of successful CC tracking was Werner score 2. Conversely, Werner score 0, severe tortuosity (>180°), acute exit angle (<90°), and length of collateral were independently associated with tracking failure. We assigned a score to each "significant" variable to create a model that showed a greater accuracy than pre-existing scores (area under the receiver-operator characteristics curve, 0.72 vs 0.65 and 0.69). Moreover, CC length was also associated with microcatheter tracking failure and complications. Werner score 0, tortuosity, acute exit angle, and CC length were independently associated with CC tracking failure, whereas Werner score 2 was a predictor of crossing success. Length of CC is associated with a higher rate of microcatheter crossing failure and complications. We combined these findings into the R-ICPS score, which showed an adequate accuracy for collateral crossing prediction.