With evidence supporting the belief that as a way of decreasing errors sentence combining offers a number of advantages for developmental writing students, a college composition instructor gave 19 developmental writing students five weeks of concentrated sentence combining study with no other instruction or writing practice. The sessions concentrated on the structures used in the students' placement essays, and punctuation was integrated into the teaching of each structure. During the first week of the class, students completed a series of exercises, two of which were paragraphs composed by the students and two of which were prepared exercises. The passages were evaluated according to four main categories: garbled construction, sentence boundary errors, comma errors, and semicolon errors. At the end of the sessions, the initial exercises were returned to the students to proofread and revise according to the techniques they had studied. They also wrote a paragraph with the same instructions as one of the two earlier writing assignments. The results of the proofreading were positive, with a decline in all kinds of errors, particularly in garbled sentences. To determine whether this proofreading ability had carried over to their writing, the pretest and posttest writing samples were compared, showing a similar reduction in errors and indicating that sentence combining can be an incisive proofreading tool for the developmental writer. (HTH)