Therapeutic ultrasound can be a very effective treatment modality when used correctly in the treatment of musculoskeletal conditions and wound healing. However, many protocols for the administration of ultrasound have not been scientifically tested. The purpose of this study was to measure muscle temperature changes during a frequently used protocol, ie., preicing prior to ultrasound application. A 23-gauge hypodermic needle microprobe was inserted 5 cm deep into the medial aspect of the anesthetized triceps surae muscle of 16 subjects. Two groups consisting of eight subjects each were tested for temperature changes during: a) ultrasound treatment on precooled tissue or b) ultrasound with no preceding treatment. Each treatment consisted of 10 minutes of continuous ultrasound delivered topically at 1.5 watts/cm2. A significant difference between the two treatment methods was measured (F = 19.06, p < 0.01). Ultrasound alone increased tissue temperature an average of 4.0 +/- .83 degrees C, whereas ultrasound preceded by 5 minutes of ice increased tissue temperature only 1.8 +/- 1.0 degrees C above original baseline level. At a depth of 5 cm, ultrasound preceded by ice treatment yielded little or no thermal benefits.