Feedlots are important in both fattening of lambs prior to slaughter and familiarizing sheep with a pellet diet prior to live export. Feedlotting is prominent in Western Australia, with 19% of prime lamb producers identifying feedlotting as their main finishing method (Connell et al. , 2002). Anecdotal reports are that temperatures within a West Australian feedlot during summer can often be in excess of 40˚C. Past research has shown that excessive heat load is a problem with feedlotted cattle (Hahn and Nienaber, 1993) and could be of particular importance when animals are being fed high energy rations; however, the extent of the problem in sheep is unknown. Previous work has shown that high temperatures lead to a decrease in feed intake and therefore productivity of the animal (Baile and Forbes, 1974). The aim of this study was to determine environmental conditions in a Western Australian feedlot during summer and to determine the core temperature of both wethers and ewes within this feedlot. The hypothesis was that sheep exposed to feedlot conditions during summer would have an increased core body temperature above normal.