This study explored the role of perinatal vulnerability (PV) in mothers and infants in relationship to the development of interaffectivity and attachment, and the relationship between interaffectivity and attachment. Participating were a low-risk sample of 74 middle-class mother/first-born infant dyads who had participated as volunteers in a combined parent-support program and research project over seven years. Infants ranged in age from 3 weeks to 9 months at time of entry, with mothers' age ranging from 26 to 43 years. Within the context of the ongoing program, the following assessments were conducted: (1) interaffectivity, through ratings of mother-infant videotaped play; (2) quality of attachment; (3) perinatal vulnerability, through structured clinical interviews with mothers; and (4) infant temperament. Findings indicated that interaffectivity and attachment were significantly correlated for the entire sample and the PV group. Although postnatal maternal illness and prenatal vulnerabilities tended to lower attachment for the group as a whole, those dyads showing higher levels of interaffectivity had higher levels of attachment. Maternal depression symptoms following birth were reported by 27 percent of the subjects; self-report of such symptoms during the first 6 months was correlated to observations at 14 months through the depression variables of the interaffectivity scale. Self-reported depression was negatively related to interaffectivity and attachment, and was related positively to previous pregnancy loss, fertility problems, and C-section delivery. Mothers reporting perinatal depression saw their infants as unusually fussy, difficult, demanding, unadaptable, persistent, and unsociable at 14 months. (Six tables detail findings.) (KB)