A study examined the effects of using heuristics, a problem-solving approach, to respond to drafts written by six university students of advanced composition in English as a second language (ESL). The students had varied language backgrounds. The teacher responded to first drafts of each of three writing assignments by writing heuristic questions in margins and at the end of the paper and providing instructions for using the questions in the revision process. The questions asked for clarification, more evidence, a more complex or coherent analysis, or more information about the writer's overall purpose. They were text-specific, open-ended, focused on content rather than form, and were limited to one to three per paragraph. Results showed that for the first two papers, the students as a group showed significant improvement. The two students rated as above average and the two rated as average writers improved at least one grade from the first to the last revision. The two rated as below-average writers did not improve as much. Results for the third, most difficult paper were not significant. Heuristics can be very effective for more advanced writers, but the focus on content alone might not be sufficient. (MSE)