The impact of environmental risk on toddlers' cognitive and linguistic development was investigated in a longitudinal study of 78 high-risk families. The risk factors examined were family social status, mother's psychosocial functioning, and quality of dyadic involvement at 1 year of age (including measures of mother-infant interaction and infant-mother attachment security). Child outcome measures included the Bayley MDI (at 24 months) and the Preschool Language Scale (at 36 months). The data indicate that dyadic involvement was an important mediator in the relation between environmental risk and subsequent child competence. Specific relations among early interactive experiences, infant attachment security, and subsequent cognitive and linguistic gain were examined within a framework of risk and protective factors. The results suggest that secure attachment may operate as a protective factor, but only among the more extreme cases in this exclusively high-risk sample.