This study focuses on the effectiveness of home visiting by specially trained paraprofessionals and nurses as separate means of improving maternal and child health. A randomized, controlled trial was conducted in public- and private-care settings in Denver, Colo. One thousand one hundred seventy-eight consecutive pregnant women with no previous live births who were eligible for Medicaid or who had no private health insurance were invited to participate. Seven hundred thirty-five women were randomized to control, paraprofessional or nurse conditions. Nurses completed an average of 6.5 home visits during pregnancy and 21 visits from birth to the children's second birthdays. Paraprofessionals completed an average of 6.3 home visits during pregnancy and 16 visits from birth to the children's second birthdays. Paraprofessional-visited mother-child pairs in which the mother had low psychological resources interacted with one another more responsively than their control-group counterparts (99.45 vs. 97.54 standard score points). There were no other statistically significant paraprofessional effects. Compared to the control group, nurse-visited smokers had greater reductions in cotinine levels from intake to the end of pregnancy. By the study child's second birthday, women visited by nurses had fewer subsequent pregnancies and births, delayed second pregnancies for longer intervals and worked more during the second year after the birth of their first child. Nurse-visited mother-child pairs also interacted with one another more responsively than those in the control group. The authors conclude that papaprofessionals trained in a model program of prenatal and infancy home visiting produced small effects that rarely achieved statistical or clinical significance, though some of this may be attributable to limited statistical power. Nurses produced significant effects on a wide range of maternal and child outcomes. Toll-free access made available with permission.