Studies on reptilian thermoregulation have been dominated by research on small diurnal lizards living in the temperate zone, in environments where thermoregulatory challenges are severe and the animals (i) consequently devote considerable time and effort to the maintenance of high stable body temperatures and (ii) are constrained in their times and places of activity by thermal factors. However, most reptiles live in the Tropics, in more thermally benign regions where the animal's ecology and behavior may be affected only trivially by thermoregulatory concerns. We present data on environmental temperatures and body temperatures of 26 radio-tracked water pythons (Liasis fuscus) in tropical Australia, to investigate the extent to which thermal considerations influence the day-to-day life of this species. Some effects are evident - for example, activity is reduced on cool nights, and gravid female pythons often bask in the few weeks prior to oviposition. Nonetheless, most pythons are able to maintain high and stable temperatures (approx. 30°C) throughout the year without overt thermoregulatory activities, because (i) ambient temperatures are generally high, (ii) microhabitats with distinctive thermal characteristics are easily accessible, and (iii) the large body sizes of adult pythons confer a high degree of thermal inertia. Overall, there are few features of the ecology of this species that appear to be substantially influenced by thermoregulation. Before we can place thermoregulatory biology in its proper perspective, we will need considerably more data on the thermal biology of tropical reptiles.