1. An artificial chicken, 'Gloria', was constructed to simulate heat exchanges of poultry during transport. Tests of the instrument in a wind tunnel showed it to have insulation properties similar to that of a live bird. 2. Gloria accompanied chickens in two types of transport modules, A (enclosed) and B (open). The average temperature difference between inside and outside the loaded vehicles when stationary and in motion were 14.0 and 7.6 for Type A and 8.8 and 6.0 for Type B. Average air movement while vehicles were in motion was 0.5 m/s for Type A and 3.3 m/s for Type B. 3. Measurements of sensible heat loss from Gloria at different temperatures and wind speeds were compared with published estimates of thermoneutral heat production and thermal insulation for well and poorly feathered chickens to estimate the range of thermal stresses likely to be experienced by chickens in transit. 4. The results showed that the combination of circumstances necessary to ensure thermal comfort for birds both at rest and in motion is very rare (e.g. only between 7 and 8 degrees C for well feathered birds in enclosed vehicles). It is, however, possible to ensure thermal comfort over a wide range of ambient air temperatures by appropriate control of air movement within the vehicle whether at rest or in motion.