The Herbst-appliance is an anterior mandibular positioner (AMP) that the Isalaklinieken in Zwolle (the Netherlands) used in 8 patients with obstructive sleep apnea syndrome or excessive snoring, who had an airway obstruction located behind the tongue base. The treatment resulted in a decrease of apnea- and desaturation index, snoring and daytime sleepiness. The treatment was well tolerated, only one patient was excluded due to mandibular joint problems. In this patient group application of the Herbst-appliance seems to be simple and effective. However, adequate diagnostics and evaluation of the outcome of the treatment are absolutely necessary because an insufficiently treated patient with an obstructive sleep apnea syndrome can experience severe cardio-vascular complications.