This study analyzes social, ethnic and regional determinants of child malnutrition, as well as the effects of access to health services in the Andean Region, through a comparison between Ecuador, Peru and Bolivia. These three countries share a profile with high stunting prevalence and strong socio-economic, regional and ethnic disparities. The analysis is conducted using DHS (Peru 1992, 1996 and 2000, Bolivia 1997) and LSMS (Ecuador 1998) surveys and it focuses on an international comparative perspective. In the case of Ecuador a detailed analysis is provided. The main task was to identify the determinants of the z-score indicators for height and weight for age. For that matter, multiple equation models were estimated, applying instrumental variables and combining different multivariate procedures, to identify the relative importance of education, housing, ethnicity and contextual regional factors as determinants of stunting in each national case. In all cases we have found strong negative ethnic effects of indigenous ethnicity as well as contextual regional negative factors for highland regions. The results remain significant even after controlling for all relevant socio- economic determinants, such as education, housing and economic status, with few exceptions.