This article assesses the effects of an integrated community-based primary care program (Brazil's Family Health Program, known as the PSF) on microregional variations in infant mortality (IMR), neonatal mortality, and post-neonatal mortality rates from 1999 to 2004. The study utilized a pooled cross-sectional ecological analysis using panel data from Brazilian microregions, and controlled for measures of physicians and hospital beds per 1000 population, Hepatitis B coverage, the proportion of women without prenatal care and with no formal education, low birth weight births, population size, and poverty rates. The data covered all the 557 Brazilian microregions over a 6-year period (1999-2004). Results show that IMR declined about 13 percent from 1999 to 2004, while Family Health Program coverage increased from an average of about 14 to nearly 60 percent. Controlling for other health determinants, a 10 percent increase in Family Health Program coverage was associated with a 0.45 percent decrease in IMR, a 0.6 percent decline in post-neonatal mortality, and a 1 percent decline in diarrhea mortality (p<0.05). PSF program coverage was not associated with neonatal mortality rates. Lessons learned from the Brazilian experience may be helpful as other countries consider adopting community-based primary care approaches.