A population-based case-control study was carried out to identify determinant factors for post-neonatal infant deaths due to diarrhea, pneumonia, and malnutrition in Greater Metropolitan Belo Horizonte, Southeast Brazil. From May 1, 1991, to April 30, 1992, 511 post-neonatal deaths due to diarrhea, pneumonia, and malnutrition were selected after investigation of medical records to validate cause of death. Of this total, 396 deaths were compared to a neighborhood control group, matched for age. The study was carried out in a low-income area with a high proportion of families living in shantytowns. The article discusses the methodology and selected socioeconomic factors. Logistic regression analysis indicated that number of household appliances, mother's and father's education, and mother's marital and work status were significantly associated with risk of infant death, i.e., they were determinants of infant deaths due to avoidable causes.