Six cases of acute transient enlargement of the parotid gland under general anesthesia, so called anesthesia mumps, are reported. Patient 1 was placed in the left lateral position and the left parotid gland was subsequently observed to be diffusely enlarged. With five patients in the prone position, bilateral parotid gland enlargement was observed. Patient 1 complained of parotid swelling. Patient 4 suffered from slight tenderness of the right parotid gland. However, the others had no subjective symptoms. All cases of parotid swelling resolved spontaneously within 7 days. Changes in serum amylase during parotid enlargement were almost within normal range. Mechanical compression by sheet amadou may have produced the swelling in the patient who was placed in a lateral position. In the prone position, changes in the autonomic nervous system during surgical procedures and anesthesia, vascular congestion resulting from the surgical position, an overactive pharyngeal reflex stimulated by endotracheal intubation and mechanical ventilation are discussed as possible causes. Evaluation of the occurrence and clinical course of anesthesia mumps provided useful diagnostic and management data.