This study examined growth in effortful control in relation to income, cumulative risk, and adjustment in 306 preschool-age children and their mothers, representing families from a range of incomes. The children were aged 3 years at baseline, and the split between girls and boys was even. Participants were recruited from a university-hospital birth register, as well as from daycares, preschools, health clinics, and charitable agencies. Families were assessed at 4 time points separated by 9 months each when the children were 36–40 months, 45–49 months, 54–58 months, and 63–67 months.