X-ray photographs of 323 white children of parents rep-resenting avg. middle class and chiefly of n. European stock were studied for development of the bones and their epiphyses at 3-month intervals from birth through 18 mos. and thereafter at 6-month and later at yearly intervals. Nine tables give the detailed findings in regard to the appearance of osseous centers and a simple chart for rating osseous development during this age period. The bone centers used as bases for this rating are shown in labeled drawings of their part of the skeleton. The percentage of children with similar ratings from 1 age period to another is tabulated. A fairly constant rate of osseous development over long periods was maintained.