The effects of routine daily separations occasioned by out-of-home care on the formation and maintenance of infant-mother attachment relationships were examined in a population of economically disadvantaged mothers. 3 groups were constituted on the basis of the time in the infant's life when out-of-home care began: (1) before 12 months; (2) between 12 and 18 months; (3) home-care controls. The infant-mother pairs were observed in the Ainsworth strange situation at both 12 and 18 months, and were classified as secure, anxious-avoidant, or anxious-resistant. Because previous research has implicated the psychological accessibility of the mother to the infant in the development of anxious-avoidant attachments during the first year of life, the hypothesis that physical inaccessibility due to out-of-home care would also be associated with anxious-avoidant attachments was tested. The data support this hypothesis. At 12 months 47% of the infants whose mothers had returned to work/school were classified in the anxious-avoidant group, while the other 2 groups did not differ significantly in the proportions of infants assigned to the 3 attachment classifications. At 18 months, differences among the 3 work status groups also showed a large portion of anxious-avoidant infants (41%) in this early working group. However, infants whose out-of-home care began after 12 months did not show an increase in the proportion of anxious attachments. Additional analyses of variables related to mother's return to work indicated that single mothers were more likely to return to work/school, that mothers who worked reported higher levels of life stress than mothers who stayed home with the infants, and that, by 18 months, both anxious-avoidant and anxious-resistant attachments were also associated with non-intact families.