Background: Differences in health and living conditions between urban and rural settings can be seen as an important example of gaps between population groups. Birth weight and child growth are important predictors for the future health of a person and at aggregate level, for the public health of a population.The general aim of this thesis is to describe and discuss birth weight, physical growth and breastfeeding of children, as well as associated factors, from birth to 24 months of age in urban and rural areas of Vietnam, thus contributing to the evidence base for health strategy and policy. Methods: Two Health and Demographic Surveillance Sites in Hanoi were used; urban Dodalab and FilaBavi in the rural part. To study rural birth weight 1999 to 2010 information was obtained for 10,114 newborn in FilaBavi. To study urban rural growth disparities 2008-2010, 1,466 children were followed for two years after birth with measurements of weight and length. A study of breastfeeding included 2,572 mothers followed for one year after delivery. Background information about households and mothers was taken from routine surveys in the two sites. Results: The mean birth weight in FilaBavi remained stable at about 3,100 grams, over the 12 years studied despite rapid economic and technological development. At the individual level we found birth weight to be associated with household economy and the education of mothers. In the urban rural comparison, the mean birth weight for urban boys and girls were 3,298 and 3,203 g as compared with 3,105 and 3,057 g for the rural infants. Children in the urban area grew faster than those in the rural area. There were markedly higher frequencies of stunting in the rural area compared with the urban. The initiation of breastfeeding during the first hour of life was more frequent in the urban area. Exclusive breastfeeding during the first three months of age was more commonly reported in the rural than in the urban area. Both birth weight and child growth were statistically significantly and positively associated with economic conditions and mother’s education. Conclusion: The results of the studies presented in this thesis show that there are large and important differences in child birth weight, child growth and infant breastfeeding between urban and rural areas. There are also major differences between the areas with respect to education and economic resources. All predictors of child birth weight and growth discussed are directly or indirectly associated with the social and economic conditions. Globalization and urbanization means obvious risks for increasing gaps between as well as within the rural and urban areas. Large discrepancies in a society will lead to serious public health problems in all segments of the population, not only the underprivileged.