Writers and writing teachers should be wary of depending on readability indexes as indicators of the difficulty of written messages. The Gunning Fog Index and the Damerst Clear Index, two readability formulas, were used to determine the readability of "A Statement of Editorial Policy" and two abstracts appearing in an issue of "PMLA." Although the passages varied widely in their readability scores, all three were considered equally readable to the intended audience. It was concluded that both the Gunning and the Damerst indexes measured readability instead of comprehensibility. Another way to view this problem is to associate "audience level" with "audience expectation." The more knowledge possessed about a particular kind of message, the less uncertain the message will be, and the greater will be the audience's comprehension of the message. Neither the Gunning Fog nor the Damerst Clear Indexes accounted for this elementary relation. Teachers can help students by studying the technical aspects of student work and by talking with experts in different technical areas to realize what readability means to different audiences. Students certainly should learn that clarity is important and that different audiences require different kinds of communication; but they should also learn that clarity cannot be quantified by counts and measures. (RL)