Though a general study of transformational grammar does not improve writing ability, students can learn to use transformational operations which combine and reduce clauses to make better sentences. Since students already know intuitively how to do the operations, transformational theory in the classroom is largely limited to sentence-combining exercises and makes no use of detailed analytical procedures. This paper demonstrates the varying complexity of typical combining exercises and then discusses their actual classroom use. In two 11th grade high school English classes, the same assignments were given, but the experimental class received instruction in sentence combining while the control class was taught in the traditional manner. A comparison of the compositions written by members of each class reveals a dramatic increase in syntactic fluency by the experimental group after only one semester of instruction. (Author)