PREFACE English 900, a course for adult students of English as a second language, contains material from beginning through intermediate levels of study. The whole series consists of textbooks, workbooks, and tape recordings, with a teacher's handbook. English 900 is one of the basic instructional courses in the Collier-Macmillan English Program. Included in the Program is a series of graded readers in which five are keyed to the vocabulary and structure of each study unit in the basic texts of English 900. The series takes its name from the 900 base sentences presented in the six textbooks. The sentences cover the basic structures and a basic vocabulary of the English language. They are introduced at the rate of fifteen in each study unit, or a hundred and fifty in each book, and are numbered consecutively from Base Sentence 1 in the first unit of Book One through Base Sentence 900 in the last unit of Book Six. These structures provide "building blocks" for all of the material studied in the series, e.g., there are approximately four variation sentences for each base sentence. As a part of his mastery of English, therefore, the student practices and learns approximately 3,600 variation sentences in addition to the basic 900 patterns. There are ten study units in each textbook in the series. Each study unit contains a group of fifteen base sentences related to a meaningful situation. In Book One of the series, the typical study unit begins with the presentation of the fifteen Base Sentences together with Intonation patterns. Questions and Answers follow and give the student practice in pairing and matching the base sentences into conversational form.