Commercial broiler chickens killed in two processing plants, one in the south of England, the other in Scotland, in two seasons (winter and summer) and on two occasions in each season, were used to investigate the effects of killing the birds immediately on arrival or holding them in lairage for one, two, three or four hours. The two most important consequences of holding the birds in lairage were that their body temperature increased and their liver glycogen was depleted. The body temperature increased with the time they were held in lairage, although most of the increase occurred in the first hour and the increase was greater in summer when ambient temperatures were higher. Liver glycogen depletion became apparent after about one to two hours in lairage. No evidence was obtained that the birds were significantly dehydrated or physically stressed by being kept longer in lairage.