INTRODUCTION: Penile curvature is the most common abnormality that is observed by men with Peyronie's disease (PD). Collagenase Clostridium histolyticum (CCH) has become a standard treatment for PD patients. AIM: To identify predictor factors associated with improvements of penile curvature outcomes in men with PD treated with CCH. METHODS: We retrospectively collected the data of patients with PD treated with CCH up to 8 injections divided into 4 cycles between January 2014 and July 2020. Per protocol, penile curvature was assessed at baseline, and after the second and ford CCH cycle. If after cycle 2, curvature demonstrated no improvement, or penile curvature was significantly improved and the patient was happy, no further treatment was recommended. However, if penile curvature was significantly improved and the patient remained dissatisfied, 4 cycles were completed. Three categories of response were evaluated: improvement (≥10 degrees or ≥20%, either 1 happens), unchanged (±10 degrees or ±20%) or worsened (≥10 degrees or ≥20%, either 1 happens). Logistic regression analyses were performed to evaluate predictive factors associated with penile curvature improvements. OUTCOMES: Degrees of the curvature changes between the baseline and after the cycles of CCH. RESULTS: A total of 114 patients underwent CCH treatment. Median age was 57 years. Median PD duration was 11 months. At baseline, mean curvature was 47 degrees, 65% had dorsal curvature, 53% mid-shaft location, and 15% calcification. After CCH treatment, the mean final curvature was 40 degrees. A total of 44% improved the curvature, 39% had no change while 17% worsened after CCH treatment. Of men who had penile curvature improvement with CCH treatment, the mean curvature decreasing in degrees and percentage were 22 degrees and 41%, respectively. Men with baseline curvature ≤ 30, 31-59, and ≥ 60 degrees, the percentage curvature improvement were 29%, 43%, and 60%, respectively. Baseline curvature was the only significant predictor of penile curvature improvement after CCH (OR 1.33, 95% CI = 1.1, 1.7). CLINICAL IMPLICATIONS: We confirmed baseline penile curvature is the most important predictive factor, and this is the first report describing proportions of penile curvature improvement with CCH treatment. STRENGTHS AND LIMITATIONS: This study has several strengths, including the use of validated instruments. Nonetheless, there are limitations: the retrospective nature of the study, a single institution; and modelling device was not controlled. CONCLUSION: Penile curvature improvement was significantly more common in patients with greater baseline curvature, reaching up to 60% for patients with ≥ 60 degrees. Flores JM, Nascimento B, Punjani N, et al. Predictors of Curvature Improvement in Men With Peyronie's Disease Treated With Intralesional Collagenase Clostridium Histolyticum. J Sex Med 2022;19:1680-1686.