Instructions are an under-researched aspect of classroom discourse. In this paper, we attempt to describe the functional structure of teacher instructions using the framework proposed by Sinclair and Coulthard (1975). We examine nine directing transactions or sets of instructions from four lessons taught on an English for Academic Purposes course at a Thai university. The directing transactions were video recorded and transcribed, and the functions identified from the teacher comments in an interview. The frequency of the various types of exchange and move in the discourse, correspondences between exchanges and moves, and pairs of exchanges and moves which co-occur significantly frequently were identified. From these, a potential structure of directing transactions is suggested. This structure starts with a boundary exchange which is followed by one or more instruction exchanges. The teacher instructions can also include insertion and inform exchanges, and usually end with a further instruction exchange. (Contains 10 tables and 3 figures.)