An introductory textbook in English as a Second Language, commonly used in Egyptian schools, was evaluated for the degree to which its stated principles for classroom use of Arabic corresponded to instructions given in the lesson notes. A computer concordance program was used to extract relevant passages from the teacher's introduction and the lesson notes. It was found that classroom practice differs from the precepts in the book's introduction in four important ways: (1) Arabic is used frequently, an average of three times per unit; (2) the range of uses of Arabic is wider in the lesson notes than in the introduction; (3) the use of Arabic for the introduction of vocabulary is much more frequent and less systematic than would be expected given the restrictions placed on it in the instruction notes; and (4) the range of vocabulary items introduced using Arabic goes far beyond that suggested in the introduction. Given the intended use of the book and the intended teacher audience, it is proposed that the effectiveness and credibility of the textbook are reduced. It is also concluded that the textbook's recommended restrictions on Arabic use are excessive. A four-stage technique for improving teaching guides in this area is outlined. (MSE)