The purposes of this research are to investigate and interpret the physical characteristics of postcranial/ infracranial skeletons of prehistoric humans from Wat Pho Sri Nai archaeological site, Ban Chiang, Nong Han District, Udon Thani Province where was excavated in 2003. The sample consists of totally 109 unearthed skeletons that were separated into two aged groups; (1) 45 skeletons of infants, children and subadult whose bones had not fused, and (2) 64 adult skeletons. The postcranial bones studied include the 1^st-5^th lumbar vertebrae, innominate (os coxae), sacrum, clavicle, scapula, humerus, radius, ulna, femur, patella, tibia, fibula, calcaneus and talus.

By utilizing the standard metric measurement and the quantitative statistical analyses, four preliminary suggestions as follow are obtained. Firstly, the linear regression function analysis that used to examined the age at death of the infants, children and subadult skeletons, the functions derived the accuracy of the age estimation about 65.3-97.7% in range. Secondly, the stature prediction of the adult skeletons calculated with the Thai-Chinese formula (Sangvichien et al. 1985), the height of the male skeletons are about 159.3-167.3 centimeters while the female height are lower than male, about 144.5-153.8 centimeters. Thirdly, the average size of at least the nine postcranial bones; the clavicle, humerus, radius, ulna, femur, patella, tibia, calcaneus and talus, of the male skeletons are significantly larger, wider and thicker than those of the female skeletons (Sig. 0.05). Lastly, based on the sex determination with the stepwise discrimination function analysis, the functions of the clavicle, humerus, radius, ulna, femur, patella and tibia derived the probability accuracy of these functions to sex assessment are about 82.9-94.9%