This paper describes a study of the teaching effectiveness of computer-assisted instruction using the PLATO system at the University of Illinois in a first level biology course. College enrollment, class rank, final grade, and time study data of the control and experimental groups were obtained from master rosters. A questionnaire administered to the experimental group the last week of each semester provided information on student acceptance of the PLATO method of instruction. At the conclusion of the study, preliminary data indicated that PLATO had the potential to become an effective educational adjunct by: (1) increasing student comprehension of lesson material; (2) actively engaging students in learning processes; (3) significantly reducing the amount of time spent by students on lesson materials; and (4) contributing to higher examination scores. Data tables and graphs and questionnaire items and responses are included. (Author/MH)