The deposition and clearance of a model substance, Tc E-HIDA, in the oral cavity/upper oesophagus and in the stomach after administration of lozenges, chewing gum and sublingual tablets has been followed by gamma scintigraphy in a group of healthy male volunteers. Following administration of sublingual tablets, the residence time of the model substance in the oral cavity was significantly longer than following administration of chewing gum. The residence time following administration of lozenges was found to be the shortest.