The prevalence of knuckle pads (callosities over the knuckles) occurring as a result of occupational exposure among 41 live chicken hangers was reported. These workers were employed in a poultry plant that processed approximately 375,000 chickens per day. Chicken hangers removed live animals from conveyer belts and suspended them from their feet in overhead W-shaped metal shackles attached to a moving monorail. Each hanger suspended about 9,000 live chickens per 10 hour work shift, with peak activity nearing 25 birds per minute. Hangers suspended chickens by grasping one leg of the bird in each hand and sliding the legs into V-shaped spaces forming the sides of the W-shaped shackles. Knuckles on both hands were at risk for striking and sliding impacts with the shackles as birds were being hung. Although all workers wore two pairs of cotton gloves to protect their hands, and nine workers wore rubber gloves over the cotton gloves as further protection, knuckle pads were observed in 56 percent (23 out of 41) of hangers. No workers in other departments were observed to have developed such callosities. No affected worker had complained of the knuckle pads and none lost work because of them. The authors conclude that the probable cause of the knuckle pads is repetitive trauma from striking and sliding the knuckles against the W-shaped metal shackles while hanging the chickens. Further study was recommended in order to develop preventive measures.