The paper examined the impact of maternal personality and maternal social support variables on the security of mother-infant attachment. The influence of maternal intelligence, affect balance, and life stress were also examined. Measures used included Loevinger's Ego Development Scale, Crnic's Satisfaction with Social Support, the Peabody Picture Vocabulary Test-Revised (PPVT-R), the Home Observation for Measurement of the Environment (HOME), Waters and Deane's (1985) Security of Attachment Q-set Procedure. Participants were 50 socially disadvantaged women and their infants. Findings provided evidence for the validity of the Q-set method for assessing security of attachment. They were consistent with Crockenberg's (1981) data indicating the critical role of maternal social support on attachment. It is of particular interest that the HOME, which was devised primarily to assess quality of stimulation provided by the parent, was the strongest predictor of secure attachment. Suprisingly, this relationship was due primarily to the contribution of a cognitive rather than an affective component of the HOME. Cognitively stimulating mothers may be more sensitive and responsive to their infants' needs. Alternatively, cognitive stimulation may itself promote secure attachment in the infant. (RH)