this study investigates the demographic and health behavior of the xavante indians of mato grosso state, central brazil. data covering the period 1999 to 2004 was collected using information from household censuses and vital statistics. in addition to standard demographic analyses, survival analysis was carried out. results show a young age structure, derived from a combination of high fertility rates (7.7 live births per woman) and declining mortality. mortality rates, especially infant mortality (97 per thousand), remain very high, surpassing regional and national rates. natural increase is the main contributing factor to population growth. the annual population growth rate is 4.4%. results suggest that recent declines in mortality and fertility may be related to transformations in the implementation of basic health care services and internal diversity, the latter of which seems to be associated with local history and sociocultural determinants.