The age-related degree of ossification of the sternum and the long leg bones (femur, tibiotarsus andtarsometatarsus) of chickens was determined both macroscopically and radiographically in ten broilersranging from 7 to 14 weeks in age, and in four laying hens of different ages and breeds. The caudal halfof the sternal crest was still cartilaginous in 14-week-old broilers. This relatively slow ossification rate ofthe sternum interfered with accurate age determination. The length of the long bones of the shank variedwith age but was also breed dependent. In contrast, the diaphyseal diameter of the long leg bones and thethickness of the articular cartilage covering the femoral head, femoral condyles and proximal tibiotarsalsurface varied little in 7 to 14-week-old broilers. The thickness of the femoral and proximal tibiotarsalarticular cartilage was more than 3 mm in broilers and less than 1 mm in the older laying hens. The closureof the growth plates in the tibiotarsus and the tarsometatarsus was the most reliable criterion for agedetermination in broilers.