The purposes of the present study were to examine associations between risk factors and the cognitive performance from one to three years of age of children living in poverty, and to investigate the protective and/or promotive effects of EHS on children's cognitive skill performance. Analyses were conducted using data from the Early Head Start (EHS) Research and Evaluation Project, a prospective study of 3001 children and families living in poverty. There were four main findings. First, children's cognitive skill scores decreased significantly from one to three years of age in comparison to national norms. Second, children whose families were on government assistance, children whose mothers had less than a high school education, children who received lower levels of cognitive and language stimulation at home, and children who had higher levels of negative emotionality evidenced more rapid rates of decline. Third, children in families who received government assistance, children whose parents were unemployed, and children whose mothers had less than a high school education had lower cognitive skill scores at three years of age. Fourth, children who were enrolled in Early Head Start (EHS) had higher cognitive skill scores at three years of age than their peers who were not in EHS. Implications for policy and early education are discussed. (Contains 3 figures and 4 tables.)