There is evidence that inflammatory processes in multiple sclerosis (MS) are age-dependent. In this study we evaluated the impact of aging on gadolinium (Gd) enhancement of brain magnetic resonance imaging (MRI) lesions in MS patients. Pre- and post-contrast MRI scans, acquired using a standardized procedure by the same MRI scanner, at least 1 month far from clinical relapse or steroid treatment, were examined in 200 disease-modifying treatment free MS patients. Seventy-three patients (36.5%) showed at least one enhancing lesion. Age at MRI examination (p=0.0001), disease duration (p=0.002) and EDSS score were significantly (p=0.02) lower, whereas relapse rate in the preceding 2 years was higher (p=0.003) in patients with enhancing lesions than in patients with unenhancing scans. Multivariate logistic analysis showed that current age was the variable better predicting Gd enhancement (p=0.004). The odds ratios were 0.95 (CI: 0.92-0.98) for each year of patient's age and 0.64 (CI: 0.48-0.87) for each age decade. The main changes in enhancement risk occurred after 35 years of age. Multivariate Poisson regression model showed that relapse rate in the preceding 2 years (p<0.0001) and current age (p=0.0003) were the best predictors of the number of enhancing lesions. This information can be used to increase the statistical power of clinical trials using Gd-enhancing lesions as an outcome measure.