Suggestions are presented in this paper to aid in the effective selection of instructional materials appropriate to the reading levels of the students who will use them. Formulas designed to predict the readability of material are discussed. The cloze procedure, which attempts to measure, for individuals, the difficulty of text, is recommended for use with instructional materials. Caution is suggested in the use of the traditional five-word deletion pattern in the case of scientific material. Alternatives to the correct-word requirement include clozentropy, a procedure whereby a reader's responses are compared against all responses placed in the blanks by a criterion group. MKM)