Synthesizing the methodologies of developmental psychology, family sociology, and systems theory, this 15-month longitudinal study examined familial role adjustments in 41 suburban families after the birth of a second child. Using interviews, observations, and rating scales, the study examined families during the third trimester of the second pregnancy, and 1, 4, 8, and 12 months postpartum. Adjustments in parent-child, sibling, and marital relations were analyzed. Rating scales included versions of the Parenting Stress Index (Form 5), the Who Does What? Index, the Questionnaire on Social Support and Satisfaction with Parenting Scale, the Rothbart Infant Behavior Questionnaire, and the Dimensions of Temperament Survey (DOTS). Selected findings are highlighted through a demonstration of how they illustrate the McCubbin and Patterson Double ABCX model of family crisis and the Family Adjustment and Adaptation Response process. Findings on parental stress and its mediation through support networks are discussed. Appendix A provides a summary of subdomains of the Parenting Stress Index, and appendix B provides a summary of temperament dimensions. (Contains 264 references.) (MM)