To investigate teaching techniques with trainable mentally retarded children, 29 day classes were visited twice; 100-minute observation periods were recorded on tape at each visit. Eight major areas of teaching methods were found: feeling tone, guidance and reinforcement, individual and group control, involvement of children in lesson, motivation, nonverbal teaching, structure of the teaching situation, and teacher centered behavior. Conclusions were that teachers spent a large proportion of time in attempting to get responses from children, acknowledging and encouraging responses, and explaining concepts and activities; nonverbal techniques were greatly used. Indications were that better teaching occurred in smaller groups which had fewer brain injured children and children who were more similar in IQ and closer in age. Of 15 major lesson categories, language development received the most emphasis while practical arts received the least. Teachers did individualize instruction but tended to work with one child only or the whole class. A teacher competency checklist and categories of lessons covering arithmetic, arts and crafts, dramatization, health and safety, language development, music, occupational education, practical arts, motor development, socialization, science, self help, social studies, sensory training, and mental development are included. (DF)