Research Findings: The Quality of Care for Infants and Toddlers (QCIT) observational measure was designed to address the need for a valid and reliable measure of the quality of caregiver-child interactions that could be used in both center-based and family child care (FCC) settings, and with diverse populations. Results from a psychometric field test of 400 classrooms indicated that the QCIT demonstrated strong evidence of reliability and validity. The QCIT was used to capture the quality of caregiver-child interactions for the professional development system "We Grow Together." Average scores improved in the QCIT Support for Social-Emotional Development domain. Findings support using this measure to assess quality and focus professional development. Additional research could use the QCIT with other interventions focused on caregiver-child interactions. Practice or Policy: The QCIT provides the field with a reliable and valid measure for examining the quality of caregiver-child interaction in licensed child care settings, both centers and FCCs, serving infants and toddlers. It also provides an evidence-based framework for selecting professional development goals that support the development of infants and toddlers.