Infants born preterm are, as a group, at increased risk for a wide variety of later developmental problems (Kopp and Parmelee 1979), although many preterm infants do well (Hack et al. 1983; Saigal et al. 1984). The perinatal vulnerability, however, is amplified in disadvantaged families (Sameroff and Chandler 1975), increasing the likelihood of later emotional and cognitive difficulties (Werner and Smith 1977). A preventive intervention project was designed, therefore, that would provide and then evaluate the effectiveness of supportive home visitor services to parents of infants who were at double jeopardy, both biologically and socially--that is, sick preterm infants being reared by low-income parents. E. Baxter, K. Weiler and I hypothesized that if intervention could increase mothers' involvement and level of responsive interactions with their children, that increased maternal commitment and responsiveness to the infant would act as a protective factor ameliorating or preventing later problems in the child (Beckwith and Cohen 1984; Werner and Smith 1982).