OBJECTIVE: To assess whether socioeconomic position, maternal intelligence (IQ), and the home environment are inter-related to cognitive development in childhood. STUDY DESIGN: Prospective cohort study (n = 723) with cognitive tests at ages 2, 4, 7, and 11 to 13 years. RESULTS: There were statistically significant positive associations of father's occupational prestige, Home Observation for Measurement of Environment (HOME) score, and maternal IQ with cognitive performance in childhood. After adjustment for confounding factors, there was an increase in cognitive development by 0.8 to 2.0, 2.9 to 4.8, and 4.2 to 9.0 points for a 10-unit increment in father's occupational prestige, maternal IQ, and HOME score, respectively. CONCLUSIONS: These results demonstrate that socioeconomic position, maternal IQ, and the home environment are independently and positively predictive of children's cognitive development. These findings provide additional rationale for implementing social policies that reduce socioeconomic inequalities.