This report describes the third year of the national Follow Through Classroom Observation study. The aims of the study were: (1) to assess program implementation at one site for each of 12 sponsors; (2) to search out the relationships between child outcomes and teaching-learning processes; and (3) to estimate which programs incorporate processes found to be positively correlated with desired outcomes. The Classroom Observation Instrument (COI) was developed to record classroom occurrences as a way to determine whether there were planned educational variations in the Follow Through programs. Report chapters discuss the structure and function of the COI, including three classes of variables used to record interactions; the criteria for the selection of classroom observers and the observer training procedures; the sampling criteria used to select specific classrooms, focus children, and focus adults; types of data analyses; and approaches to relating classroom processes to child test outcomes. Appendices, which make up about half the document, include the Classroom Observation Instrument, the factor analysis variable list, classroom observer comments, changes in classroom observation variables from 1970 to 1971-72, and other statistical data. (SET)