The increase in the number of infants and toddlers experiencing nonparental care creates an urgent need for the insights of theorists, clinicians, and researchers. These insights can help caretakers promote the mental health of infants and toddlers. Although caregivers usually provide sufficient support of babies' cognitive development, they may not attend to children's emotional and social functioning. Several theories help clarify the characteristics of infant and toddler emotional development. Erik Erikson identifies infant dialectical problems of acquiring basic trust, a secure sense of autonomy, and the ability to exercise choice. Margaret Mahler describes stages in infant emotional growth and development in relation to modes of maternal care. Attachment theory and ethological theory also offer explanations of infant development. Mary Ainsworth's Strange Situation technique has become the major measure by which infant attachment is determined, and attachment research provides subtle tools for detecting emotional distress by attending to an infants' body cues, such as compulsive rocking or inconsolable crying. Caregivers can make changes in the environment and routines to alleviate infant distress. In addition to logistical and environmental policies that support infant mental health, caregiver behaviors, such as massaging an infant or singing softly, can enhance personal interactions. Parents and caregivers should work together to prevent potentially disturbing emotional effects of nonparental, full-time care in early infancy. (MM)