Teacher involvement in the development of instructional materials for Trainable Mentally Retarded (TMR) children and the criteria to be considered in developing these materials are discussed. Among the topics presented are (1) the TMR teacher's awareness of pupil needs, (2) the applicability of materials to teaching style and learning style, (3) the teacher's enthusiasm in trying out the materials, (4) the need for more special materials for the TMR child, (5) the evaluation and modification of materials developed, and (6) the opportunities for pupil involvement. It was concluded that objectives should be stated in operational terms. Materials should be developmental and sequential, should include the theories and principles of learning, should fit the teacher's teaching style and the child's learning style, and should relate to the social level at which the TMR child is functioning. The materials should have intrinsic appeal. A list of references on training the TMR child is provided. (Author/NS)