Readability formulas can be useful tools in accomplishing their primary purpose--to give very general estimates of difficulty. Unfortunately, there has been a great deal of misunderstanding regarding their use, which has resulted in misuse and abuse. The formulas were designed to be applied post hoc to existing materials. They were not intended to serve as guides for writing. Publishers, eager to guarantee that their materials are suitable for indicated student populations, require writers to "write to formula" or later make revisions if grade level designations are too high. Many believe that readability formula scores can be used in conjunction with the grade equivalency scores students achieve on standardized reading tests to effect an appropriate match between reader and text. Such a belief is unsupported in fact. Given the imprecise nature of both the formulas and the test scores, it is ultimately the teacher's responsibility to select appropriate reading material for his or her students. Interest and motivation, neither of which is taken into account by the formulas, are key factors in determining what a student will or will not read, and will or will not comprehend. Formulas can yield useful information, but only teachers themselves can take into account the many factors that affect their own students' comprehension and make better judgments on this basis than are possible on the basis of formula scores alone. (Some suggestions for enabling students to comprehend are included.) (HOD)