Thirteen male instructors were monitored during a total of 44 live fire training exercises (ambient temperature 74+/-42 degrees C). Exposure time during the 'Hot Fire' (HF), 'Fire Behaviour' and 'Fire Attack' exercises was 33.0+/-7.9 min (n=30); 26.3+/-5.5 min (n=6); and 7.3+/-2.6 min (n=8) respectively. At the end of the exercises, mean core temperature (t(core)) was 38.5+/-0.9 degrees C (n=32), however eight instructors had a t(core) above 39 degrees C. The mean maximum temperature under the fire hood was 41.2+/-4.6 degrees C (n=40). Mean maximum heart rate (HR) was 138+/-26 bpm (n=34) however, in five exercises, HR exceeded 90% of the instructors' HR reserve. Mean fluid deficit was 0.62+/-0.6 l (n=30) at the end of the HF exercises, the maximum being 2.54 l. Four instructors doubted their ability to perform a rescue at the end of the exercise. The energy cost of performing simulated rescues of a 50 kg dummy in the cool was investigated in a pilot study. Mean HR during the rescues was 79+/-7% of the instructors' HR reserve and it was estimated that this could increase t(core) by 0.4 to 0.6 degrees C. The physiological responses to the fire-fighting exercises varied considerably and reflected the differences in work performed and external heat load. The results obtained from some individuals give cause for concern, and signs of heat strain were seen in at least two individuals.