Calorimetric measurements have been made for broiler chickens in a commercial transport vehicle. A standard poultry transport vehicle, which consisted of a lorry and drawbar trailer combination, was equipped with ventilating fans and the air movement restricted to a single inlet and single outlet arrangement on each of the two elements of the vehicle. Measurements of temperature, relative humidity and the concentration of carbon dioxide ( CO) were made at the inlets and outlets for a known set ventilation rate. For the calorimetry, the fully laden vehicle was held stationary for a period of 2 h prior to the birds being unloaded into lairage. The measurements showed that there was a signi"cant period before heat production stabilized, particularly, on the lorry, where conditions during transport were not controlled. The inadequacy of natural ventilation on the trailer required fan ventilation to operate at all times and hence conditions on the trailer were more stable. Once stability had been reached, the sensible and latent heat production were measured, together with the CO production. The calculated respiratory quotient was consistent with values derived elsewhere for adult fowl in a fasted condition. A minimum design ventilation rate based on liveweight is proposed subject to uniformity of ventilation throughout the vehicle.