Heat and moisture production rates (HP, MP) of modern broiler chickens (Cobb strain males) raised on litter in commercial production housing were determined from extensive environmental and production data of 20 house–flocks. The flock size was 18,800 birds, with a typical growth period of 56 days. Regression equations were established that predict total, sensible and latent HP of the broiler houses over common ranges of body mass (0.4 to 3.2 kg), house temperature (20 to 32C), relative humidity (30–80%), and photoperiod (light or dark). Specific total HP rate from this study was up to 31% higher than found elsewhere at 0.4 kg body mass, and the difference diminished as mass approached 2.3 kg. Modern broiler houses have reduced MP that presumably resulted from use of nipple drinkers as opposed to trough drinkers on which most of the literature data were based. The new HP and MP data are expected to enhance efficient design and operation of modern broiler housing ventilation systems. The results further confirm the need to systematically update literature HP and MP data for engineering practices.