This study examined the effect of age on bone breaking strength and the prevalence of broken bones in hens kept in a perchery egg laying system. During the first 6 weeks of lay, bone strength increased by about 25%. The prevalence of broken bones which had repaired increased from 0% at 19 weeks of age to 23% at 72 weeks. Most of this increase occurred during the last half of lay and during this period the humerus became slightly more brittle. The exact reason for the increase in broken bones was not revealed, but because they occurred largely in the keel and furculum they were thought to be due to flight and landing accidents.