A summary of tumour temperature data obtained from 31 patients who underwent 147 hyperthermia treatments with the Sonotherm 1000 ultrasonic system is presented. The treatment goal was to achieve a minimum of 42.0 degrees C in tumour for 60 min duration with normal tissues remaining below 43.0 degrees C. In 83% of treatments at least one measured tumour temperature reached or exceeded 42.0 degrees C at some time during the treatment. Nineteen per cent of these treatments had a time- and spatial-averaged temperature (measured in tumour) greater than or equal to 42.0 degrees C. A variety of anatomical sites were treated and these were grouped into four categories: groin/trunk, axilla, breast/chest wall and head/neck. Measured temperatures in tumours located in the groin and trunk sites were significantly higher (22% greater than or equal to 42 degrees C) than other locations. The head and neck treatment temperatures were significantly lower (8% of measured points greater than or equal to 42 degrees C.