Readability formulas were originally conceived of as being evaluative measures. However, if a text is being rewritten or revised so that it matches a particular level of ability in its intended readers, it is rather inescapable that readability formulas will influence the changes made. Tacitly or not, formulas now are used to diagnose what causes difficulty in reading. If they are used this way, they can only give wrong answers to the question of what changes should be made in a text to make it easier to read. Changes should be made in a text because of inherent difficulty or problems of ambiguity in that text, and not just to influence the score that the text will receive via readability formulas. Any changes that require knowledge of language, literary style, and the ability to express ideas in the best way to communicate the content and logical relations of the text should be left to the writer or editor. A comparison of two versions of four texts--the original and an "easier" adaptation--shows clearly the influence readability formulas now exert on textbook preparation. Among the deleterious changes found in the analysis were the deletion of connectors; loss of causal and other relations between parts of a sentence; loss of background, focus, and topic information; and changes in points of view. (FL)