This state-of-the-art paper and its accompanying 42-item annotated bibliography are on classroom observation systems in preparing school personnel. The paper is divided into four parts: (1) Introduction; (2) Description of Selected Classroom Observation Systems; (3) Use of Classroom Observation Systems in the Preparation of School Personnel; and (4) Summary and Conclusions. Part 2, the most detailed section, describes the more important classroom observation systems (i.e., "organized and systematic attempts to assess and quantify through observation the behaviors of teachers and students engaged in the teaching-learning process"). These systems are grouped in three categories: affective systems (those concerned primarily with the emotional climate of the classroom); cognitive systems (those concerned primarily with intellectual activities which result in the improvement of cognitive processes and skills); and multidimensional systems (those which attempt to assess both the affective and cognitive domains). Among the conclusions suggested by this comparative study are that classroom observation systems (of which the affective ones have been most widely used) can be used profitably in conjunction with microteaching, role playing, and other preservice laboratory teaching experiences; that, through their emphasis on teaching behaviors and indirect teacher influence, they have contributed to a greater emphasis on laboratory experience in teacher preparation and to an increasing "humanization" of teaching. (JES)