This project developed and examined the validity of a tailor-made life events checklist specific to the experiences of adolescents in stepfamilies (i.e., the Stepfamily Events Profile; STEP). The STEP was developed from information gathered in focus groups and interviews and includes positive and negative events that are meaningful to adolescents in stepfamilies. The STEP was given to 90 adolescents residing with their biological mother and stepfather. Negative events were significantly related to adolescent report of maladjustment, and positive events were significantly related to mother and adolescent report of internalizing problems, above and beyond the effects of several covariates. Also, the effects of negative and positive events were uniquely predictive of adolescent maladjustment. Events reflecting interactions within the adolescent's dyadic family relationships were most strongly predictive of adolescent maladjustment.