PURPOSE: To ascertain the incidence of proximal humeral epiphyseal ossification centers, as shown on chest radiographs, in neonates and infants. MATERIALS AND METHODS: The distribution of corrected age(CA) of the infantswas from 24 weeks of gestational age to 6 months of postnatal age. They were obtained from inborn and outborn infants without developmental problems. Proximal humeral epiphyseal ossification centers were evaluated by two radiologists from a total of 440 chest radiographs. Of these, 196 were of the female chest and 244 were of themale. Corrected ages based on postnatal age are expressed as weeks before two months of age and as months after two months of age. The ossified or nonossified epiphyses of the humeral heads were plotted against corrected age. From these graphs, the percentages of ossification according to their corrected age was observed. RESULTS: 37weeks of corrected age in which 9.1%(1/11) was ossified was the earliest age of humeral epiphyseal ossification in the female. While 35 weeks of CA in which 6.3%(1/16) was ossified was the earliest age in the male. In full-term neonates(=40 weeks of CA), 20%(6/30) of epiphysis was ossified in the female and 23.3%(7/30) in the male. The female group of 43-44 weeks of corrected age showed ossification of 50% and the male group of 44-45 weeks of corrected age showed ossification of 50%. By five months of corrected age, 100% of epiphyses, both in the female and in the male, were ossified. CONCLUSION: Humeral ossification centers are seen from 35-37 weeks of correctedage. By five months of age, all humeral epiphyses are ossified.