Computer assisted instruction in Latin and in English vocabulary development, which is used at the University of Illinois-Urbana, is described. The computer portion of the beginning Latin course consists of 40 lessons which provide drill and practice in vocabulary, morphology, and syntax. The program can be used either as a classroom supplement or as part of an independent study course. Each of the 40 lessons has four sections--vocabulary, morphology, translation, and a self-test. Work on PLATO counts as one-quarter of the total course grade and is designed to increase efficiency in study and lengthen retention. The Latin composition program is designed as a complete review of Latin grammar through the medium of prose composition and can be used at any time after the first year of college or first 2 years of high school Latin. The program contains 31 lessons, which may be used separately from each other or in sequence, either as a classroom supplement or an independent study. Each lesson is divided into four parts--morphology, composition exercises, vocabulary, and a diagnostic self-test. In addition, a course in the enlargement of students' English vocabulary through the study of Latin and Greek roots and their derivatives uses a PLATO component. Advantages of PLATO-based instruction include: (1) the student has a choice of study areas and the sequence of the work; (2) immediate reinforcement or correction is provided; (3) drill items are randomized to reduce serial learning; (4) responses are stored by the computer and further work is determined on the basis of these replies; (5) sentence responses are judged at the orthographic, lexical, and syntactical levels; and (6) diagnostic tests are provided. (SW)