The development of a national program to assure access to prenatal care for all women, regardless of income, is believed to be an effective means of reducing low birthweight and neonatal mortality in the U.S. Yet scarce empirical evidence concerning the effectiveness of large-scale prenatal care programs is available. This paper summarizes an evaluation of a statewide public prenatal care program which grew out of the federal Improved Pregnancy Outcome (IPO) project. Using linked birth and infant death-certificate data, and IPO program records from a four-year period (1985-1988), this study compares the neonatal mortality rates of participants of Florida's IPO program with those of a matched comparison group. The results indicate an inverse relationship between IPO participation and the risk of neonatal mortality in a low-income population. These findings suggest that large-scale prenatal care programs can be effective in improving birth outcomes.