The possible effects of ultrasonic scaling of all maxillary teeth for a total of 5 min on the inner ears of 20 healthy young adults, 22-36 years of age, were investigated by means of pure tone audiometry. Audiograms were obtained just before and immediatley after scaling. Temporary shifts in hearing threshold (TTS) of 10-20 dB, mostly at 7--8 kHz, ersisting for up to 30 min, were recorded in eight of the individuals. Three patients reported high-pitched tinnitus lasting for 20-30 min after ultrasonic scaling. When audiograms were obtained 3--5 weeks later in the same 20 individuals before and immediatley after they had kept their mouths open for 5 min, but with no scaling performed, TTS was recorded in three of the individuals. TTS after opening only was less pronounced than TTS after ultrasonic scaling, both with regard to severity and duration.