The Global Assessment of Severity of Epilepsy (GASE) Scale is a single-item, 7-point global rating scale designed for neurologist-report of overall severity of epilepsy in children. Preliminary evidence suggested it may be valid and reliable for research and clinical use. Data from the Health-Related Quality of Life in Children with Epilepsy Study (HERQULES) was analyzed to evaluate validity, stability, and responsiveness of GASE scores. Spearman’s Rho indicated that GASE was moderately correlated with key aspects of epilepsy but weakly correlated with parents’ perceptions of child health. Frequency and intensity of seizures and interference of epilepsy or drugs with daily activities were most strongly correlated with GASE. Intra-class correlation coefficients (ICC) provided modest evidence that GASE could detect stability. Distribution- and anchor-based indices suggested that GASE was responsive to changes in clinical criteria. Results support the construct validity, stability, and responsiveness to change of the GASE Scale in children with epilepsy