Construction, administration, and interpretation of an informal reading inventory is, perhaps, too time consuming a task for the classroom teacher who may decide that other activities are more relevant. The informal reading inventory will probably be built into basal materials or into diagnostic batteries. However, the teacher can develop other diagnostic tools that will add to his effectiveness in a reading program which already has formal diagnosis and individually prescribed instruction. The teacher can observe reading behavior, diagnose problems, prescribe measures for solution, and teach, making revisions as needed. An example of diagnosis and prescription of one specific problem is included. (MD)