Information about 255 children and adults with Pompe disease was gathered thr ough a questionnaire. Disease severity was associated with disease duration and not with age; an early manifestation of the disease implied earlier wheelchair o r ventilator dependency. The patient group under age 15 included a subgroup with a more severe and rapid course of the disease. They require more intensive foll ow- up and early intervention, before irreversible damage has occurred. Information about 255 children and adults with Pompe disease was gathered through a questionnaire. Disease severity was associated with disease duration and not with age; an early manifestation of the disease implied earlier wheelchair or ventilator dependency. The patient group under age 15 included a subgroup with a more severe and rapid course of the disease. They require more intensive foll ow- up and early intervention, before irreversible damage has occurred.