This study is a controlled evaluation of the efficacy of home visits designed to promote better child health and development for infants of working class families. Each of the 115 mother-infant pairs meeting the study criteria was assigned to one of three comparable groups: group A received home visits starting prenatally; group B received visits from six weeks post partum; and group C received no visits. Home observations were completed by an independent evaluator at 6 weeks, 6, 12, and 18 months of age. Significant differences favoring group A over groups B and C were found at each evaluation period. These included: (1) a reduced accident rate; (2) higher scores on assessments of home environment and maternal behavior; and (3) a lower prevalence of mother-infant interaction or feeding problems and of nonparticipant fathers. Aside from a reduction in the accident rate, group B did not benefit from the home visits when compared to control infants. The results support the efficacy of home visits, but only if a prenatal visit is included. These findings suggest that a unique relationship is created between the mother and home visitor and this relationship is sensitive to the timing of the initial encounter.