The effects of altitudinal variation on child growth and development have long been a focus of research for students of biocultural mechanisms of adaptation to high altitude. Early studies in Peru showed that children born and raised at altitudes above 3500 m tended to exhibit reduced birth mass, slower growth rate, longer overall period of growth, poorly defined adolescent growth spurt, and delayed onset of certain aspects of psychomotor development; it is difficult to state with certainty whether these phenomena reflected developmental acclimatization to hypoxia or represented an inherited pattern of development. In contrast, more recent studies in Ethiopia showed that children living at high altitudes were taller and heavier, and matured earlier than their genetically similar counter-parts living at low altitudes. The degree of hypoxic stress encountered at the altitude of the highland communities in Ethiopia (3000 m) may not be great enough to adversely affect growth; however, other environmental variables, such as the increased incidence of infectious disease at lower elevations, may be involved. In order to further clarify the effects of genetic and environmental influences on growth among high altitude populations, the growth characteristics of peoples of Tibetan origin living in Nepal were studied. Anthropometric, radiographic, and demographic data were collected from residents of various Sherpa communities in the Everest region of Nepal, and from a group of Tibetan refugees living in the vicinity of Kathmandu. Results of this study indicate that the growth of both groups is extremely retarded by U. S. and European standards. Although the refugee children were slightly more advanced in most growth indicators than the Sherpas, the difference was probably not as great as that existing between high and low altitude populations in Peru. Moreover, the refugee children lived under more favourable conditions in terms of nutritional and health benefits than the conditions of the Sherpas, but were considerably more retarded in all growth indicators than the indigenous inhabitants of highland Peru or Ethiopia. The Nepal data demonstrate that the growth characteristics of Himalayan peoples may reflect the presence of an extremely ancient Tibetan gene pool. A comparison of the three studies shows that, while hypoxia and other environmental agents do influence certain growth parameters, specific effects demonstrated in one high altitude population cannot be directly applied to another. Some differences in the growth characteristics of these populations may be caused by the interaction of as yet undetermined environmental agents, but genetic influences on growth may be more important among high altitude populations than hitherto suspected.