By applying R. S. Lazarus's (1993) theoretical model, the authors explored the dynamics of stress and coping as central mechanisms underlying parenting adjustment and infant development. Longitudinal assessment of 140 primiparous mothers included measures of cognitive appraisals of parenting, coping strategies used, and supportive coping resources at pregnancy and 1 month, 6 months, and 12 months postpartum. Maternal outcome measures of adjustment included maternal well-being, parental efficacy, and observed behaviors of caregiving and affiliation. Infant developmental outcome was measured by the Bayley Scales of Infant Development (N. Bayley, 1993). All measures of the stress and coping model showed systematic developmental changes across the transition to parenthood as well as relative stability of individual differences. In addition, the stress and coping variables were found to have additive and interactive effects in predicting both maternal adjustment and infant development.