Even though readability formulas are being used more widely than ever before in schools, libraries, businesses, newspapers, and government, there are critics who argue against their use. Criticism includes blaming the formulas for the "dumbing down" of textbooks, for being poor writers' guides, and for not taking into account the background or motivation of the writer. However, there is much evidence that readability formulas are valid. They will predict (are correlated with) comprehension using traditional multiple choice questions, comprehension using cloze passages, oral reading errors, readership, subvocalization, eye voice span, functional chaining, and controlled subjective judgment. Other reasons for the dislike of readability formulas may include the wish for something to blame about the way textbooks are written, the fear that they stifle creative writing, their objectivity, or the discovery of other factors that bear on reading difficulty. Despite the criticism, research on readability formulas suggests that they are doing what they are supposed to do and have helped millions of people in many nations who, as a result of these formulas, have more suitable textbooks, consumer contracts, and newspapers. A short list of references concludes the document. (EL)