This study examined the prevalence and determinants of spanking of children at 3?years of age and the associations between spanking and externalizing behaviour and receptive verbal ability at age 5?years. Overall, we find maternal spanking rates of 55.2% and paternal rates of 43.2% at age 3?years. Mothers facing greater stress and those who spanked earlier are more likely to spank at age 3?years, whereas those who report a supportive partner during pregnancy and those who were not US born were less likely to spank. Mothers and fathers in communities where spanking was more normative were more likely to spank. Fathers were less likely to spank daughters at age 3?years. Frequent maternal spanking at age 3?years was associated with externalizing behaviour and receptive vocabulary at age 5?years, controlling for an array of ecological risks, earlier behaviour and verbal capacity. Taking advantage of the large and diverse sample, we explored potential interactions and found no evidence that race, parental warmth, normativeness or child gender moderated the association between spanking and externalizing or receptive vocabulary. These findings add to the literature on negative consequences associated with a widely endorsed parenting practice and highlight the need for research that explores alternative effective discipline practices and addresses parent questions of what else they could, or even should, be doing.