The literature on cold stress in permanent high altitude residents and sojourners in the Himalayas and Andes is reviewed. High altitude natives, as exemplified by Peruvian Quechua Indians, are relatively well protected from the cold by the efficient use of wool clothing. However, exposure to wet-cold and dry-cold conditions is present, both diurnally and seasonally. Basal metabolism in the native is slightly elevated over United States norms, and natives are able to maintain high levels of blood flow to the extremities during whole-body and local extremity cooling tests. There is suggestive evidence for a developmental pattern of acclimatization to cold, but definitive evidence for genetic tolerance to cold in the highland native is lacking.