The conditions of day care quality under which infants direct secure attachment behaviors toward their day care providers were examined. Two groups of 12- to 18-month-old infants, who were experiencing either 1:4 or 1:7 caregiver-to-infant ratios, and their day care providers, were observed while they interacted in their day care centers. Caregivers' effectiveness in caring for the infants, and infants' attachment behaviors toward the day care providers, were assessed. Results showed that infants cared for in groups with more favorable ratios had more effective caregivers, and were thus more likely to direct secure attachment behaviors toward day care providers. Group size had a similar effect on infant and caregiver outcome measures, with smaller groups being associated with more effective caregiving and more secure attachment behaviors. For infants in groups with less favorable ratios, continuity of care in the same day care center was more important for the expression of secure attachment behaviors toward day care providers than was continuity of care with the same caregiver. Girls' day care providers were more effective than boys' providers, and girls, in turn, were more likely than boys to direct secure attachment behaviors toward their day care providers. (Author/SH)