Background. The classification of coronary lesion complexity, using the American College of Cardiology/American Heart Association (ACC/AHA) is a predictor of balloon angioplasty success. Stents have improved results even in complex lesions. Aim. To compare the ACC/ AHA and the new Society for Cardiac Angiography (SCAepsilonI) coronary lesion scores as predictors of angioplasty success. Patients and Methods. Alí consecutive angioplasty procedures (n=346, 456 lesions, 47% stents) were prospectively analized from August 1996 to March 1999. Coronary lesions were classified using the ACC/AHA and SCA&I scores. Angiographic success was assesed and its multivariate predictors determined with logistic regression analysis. Results. According to the ACC/AHA score, angiographic success was 97, 92.7, 93.3, and 82.3% in A, Bl, B2 and C lesions respectively (p=0.013). There only were significant differences in success between C and A, Bl or B2 lesions. According to the SCAepsilonI score success was achieved in 97.3, 97.9, 75.8 and 33.3% in nonCP, CP, nonCO and CO lesions respectively (P<0.001). With the SCAepsilonI score statistically significant differences in angiographic success were found for all lesion score comparisons, except between nonCP and CP lesions. No other variables had predictive value for angiographic success. Conclusions. Coronary angioplasty angiographic success is better predicted by the new SCAepsilonl lesion score than with the ACC/AHA lesion clasification in a group of patiens with frequent use of stents. (Rev Méd Chile 2001,129: 605-10)