INTRODUCTION: The clinical course of late-onset Pompe disease is heterogeneous, and new clinical outcome measures are needed to evaluate enzyme replacement therapy (ERT). METHODS: We correlated the 6-Minute Walk Test (6MWT), Walton and Gardner-Medwin (WGM) score, and GSGC (Gait, Stairs, Gower, Chair) scores in 40 patients. RESULTS: At baseline, the GSGC score correlated with both WGM (P < 0.001, n = 33) and 6MWT (P < 0.001, n = 26). After 1 year of ERT, we observed a significant change in gait, stairs and chair performance on the GSGC scale. The 6MWT significantly increased from 319 to 371 meters in 32 patients, and the WGM score was reduced. CONCLUSIONS: GSGC is a group of functional tests that requires only a few minutes to perform, therefore, this score might be a good indicator to be used in future studies. Muscle Nerve 45: 831-834, 2012.