This paper reports on the development and validation of the Assessment Profile: Research Version, an observation checklist containing 87 items that reflect developmentally appropriate practices in early childhood programs. The Assessment Profile provides quantitative measures of classroom environments and teaching practices which facilitate the development of young children. The profile consists of five scales: (1) Learning Environments; (2) Scheduling; (3) Curriculum; (4) Interacting; and (5) Individualizing. The Assessment Profile was formed by selecting those items with the highest discriminating ability from the Assessment Profile for Early Childhood Programs. Content validity was established by expert review and by cross-referencing the content of the Assessment Profile with the accreditation criteria of the National Association for the Education of Young Children. The concurrent validity of the Assessment Profile with the Early Childhood Environment Rating Scale (ECERS) was examined in two studies that used samples of children in 53 and 120 preschool classrooms. Results indicated a correlation between the scales of the Assessment Profile and the scales of the ECERS and the ECERS total score. (MM)