A study examined the effects of an instructional intervention designed to improve high school students' ability to comprehend the gist of biology text materials. Subjects were divided into a strategy group, a read-study group, and a control group. The strategy subjects were given eight days of instruction in a procedure designed to help them analyze material sentence by sentence, look for relationships between ideas, and then extract the gist. The read-study subjects merely practiced the task of reading short passages, studying the information, and then recalling it. Subjects were given five test passages throughout the experiment, four biology and one history, and asked to produce an unprobed recall, answer six questions on main idea content, and rate their level of familiarity with the passage content. All subjects were tested before, during, and after the instructional period. The results did not support any one experimental condition over the others, but indicated certain commonalities between the two treatment groups, including the following: (1) those who recalled more total information also recalled more of the important ideas, (2) those who excelled did so throughout the entire experiment, (3) recall ability increased for the subject who excelled in each group. However, the recall of the strategy subjects tended to be more alike than that of the read-study subjects, and the lower-achieving strategy subject showed greater improvement on the question-answering tasks than did the lower-achieving read-study subject. The results reflect the need to consider individual student differences in comprehension in the classroom. (HTH)