This paper describes the 2-year evolution of an ongoing program of inservice training for public school personnel designed to train observers in the use of a systematic observation technique--the Reciprocal Category System. The 605 participants include teachers, librarians, administrators, and central office personnel. Nine aspects of the four training sessions are discussed with respect to the three major headings of "organization,""training procedure," and "observer competence." Under the category of organization, training time, group size, and training sequence are considered. A training time of two days is developed, while a comparison of results by group size indicates that large groups are as effective as small groups. Training procedural concerns include development of a manual, revised twice; content, which shifts in emphasis from concepts and theory to skills and calculations; and trainer use. Observer competence elements include types of instruments--a concept test and a skill test--and the improvement made in these two instruments. The paper concludes that it has been found possible to train large groups of observers in two days to a responsible level of accuracy in the use of the Reciprocal Category System for classroom observation for purposes of classroom self-analysis. (RT)