A simple technique for measuring comprehension of lengthy prose, i.e., consisting of multiple sentences, is presented. The “textual segmentation” procedure requires subjects to partition text into complete, meaningful units, such as paragraphs, chapters, and books. Very easy to prepare, administer, and score, textual segmentation has potentially wide application as a measure of reading comprehension, as a means for studying how people segment prose into paragraphs and the like, as a readability measure, as an instructional tool, and as a criterion for judging the success of text-reading and text-writing computer programs in research on artificial intelligence.