The development and initial validity and reliability testing of a single-item, 7-point global rating scale designed for neurologists to assess the overall severity of epilepsy in children, the Global Assessment of Severity of Epilepsy (GASE) Scale, is described. The GASE Scale was quick and easy to use. Median epilepsy severity in the development sample was 3 (moderately severe), with a range from 1 ("not severe at all") in 36 patients (26.9%) to 7 ("extremely severe") in 7 patients (5.2%). Preliminary evidence of construct validity was found in support for our a priori predictions of associations between GASE scores and neurologists' ratings of seven individual clinical aspects of epilepsy and in a cumulative R(2) for the GASE score of 81% using ratings of the clinical aspects of epilepsy. Weighted kappa was 0.85 (95% CI: 0.79, 0.90) for inter-rater reliability and 0.90 (95% CI: 0.82, 0.98) and 0.95 (95% CI: 0.91, 0.98) for test-retest reliability for each of two raters. These promising initial results support continuation of the multistage process of testing the validity and reliability of the GASE Scale within various clinical contexts.