This document describes the development of an observation instrument which could provide an objective record of the content of the learning environment in the early childhood classroom. A team of early childhood specialists explored the critical dimensions of the preschool experience and developed a series of descriptive categories in terms of objective, observable events and materials. The literature on classroom observation was also reviewed. Data was analyzed in terms of frequency distribution programs, reliability programs, factor analytic studies and interpretations. Almost half the report is comprised of tables. (MS)