To examine the effects of infant negative emotionality and of mothering and fathering during the toddler years on 3-year-old boys' externalizing problems and inhibition, as well as explore the proposition that children vary in their susceptibility to rearing influence, 125 first-born, Caucasian boys from maritally intact families were studied. Results revealed that when infant negativity is measured with objective, replicable, and discriminantly valid procedures, no relation obtains between it and externalizing problems (nor inhibition). Moreover, as hypothesized on the basis of prior work, parenting was a stronger predictor of externalizing problems and inhibition in the case of children who were highly negative as infants. Mothering proved a stronger predictor of externalizing problems and fathering of inhibition, with more negative mothering in the 2nd and 3rd year forecasting higher CBCL-externalizing scores and less negative fathering in the 2nd and 3rd year and more positive fathering in the 2nd year forecasting more inhibition at age 3. Implications of these findings for studies of parental influence are considered.