The coding language INSTRUCT is a high-level programing language designed for programing computer-assisted instruction lessons. As it is presently implemented on the PDP-10 computer, a "lesson processor" transforms the INSTRUCT lessons into a numeric code that can be understood by a teaching program called INST. INST controls the interaction between the student and the computer at the time the student is taking a programed lesson. The main steps in preparing an INSTRUCT lesson are: coding the lesson, assembling the lesson, correcting assembly errors, reassembling, loading, and debugging. This manual is designed both as an instructional manual for beginning coders and as a reference manual for the INSTRUCT coding language. It provides an overview of the language, a definition of the INSTRUCT commands, directions for processing and debugging INSTRUCT lessons, and instructions for advanced coding techniques which expand the routines available from the INST program. (JY)