Background: Social and economical inequalities have an adverse effect on infant mortality. Aim: To test if the poorest communities of Santiago have the highest rates of infant mortalilty. Material and methods: Variables were obtained from the year 2000 Vital Statistics yearbook and the National Socioeconomic Characterization inquiry. Infant mortality was correlated with the mean income of households, the population below the threshold of poverty and the unemployed population of the 32 municipalities of the Santiago Province. The ratio and the difference in mortality rates between the communities with the higher and lower incomes and the attributable population risk for infant mortality in the Province of Santiago was calculated. Results: Infant mortality was positively correlated with the population below the threshold of poverty (r=0.383; p=0.03) and the unemployed population (r=0.437; p=0.012) and inversely correlated with the mean household income (r=-0.522; p=0.002). Infant mortality in the poorest community was 2.2 times higher than in the richest one. The difference in rates was 6.6/1000 live births. The attributable population risk determined that it is possible to reduce infant death by 57.8%. Conclusions: In the Province of Santiago, the poorest communities have the highest infant mortality (Rev Méd Chile 2004; 132: 461-6)