A principal aim of the study was to examine schoolteachers’ evaluations of current computer-based teaching packages. The decisions which guided the utilization of this material in the classroom, the contributions it made to learning, and what teachers themselves gained from the experience, were also of significant interest. Four secondary schools were the main participants and their staff agreed to examine and use current programs, where they could, in classroom teaching. Ninety-one packages (covering Mathematics and the Physical, Biological and Social Sciences) were obtained from publishers and other sources; one, three or six microcomputers were made available for class use. Twenty-eight programs were judged to be of interest, 15 sufficiently so to be applied in teaching, and 22 lessons were observed over a 6-month period. Data were collected by interview, questionnaire, classroom observation schedules and by pupil questionnaires, worksheets and post-tests. In making their choices, teachers were particularly concerned with relevance of programs to their courses, flexibility in accommodating different modes of teaching and degrees of user sophistication, and presentation of feedback and data at the terminal. In planning the use of programs, teachers aimed for hand-on experience through group work, although the working methods and composition of such groups were important if less able pupils were to benefit. The programs were well received and generated interest; however, data also showed that reducing assimilation problems by using computer-based tasks in directed ways which replicate conventional teaching sequences, meant that simulation programs could become mere providers of data and learning gains could be relatively modest. An extensive comparative experiment supported these conclusions. On occasions when more open initiatives were encouraged, teachers tended to underestimate pupil preparation, particularly as current programs carry little supporting help and teaching. The implications of these results for program development, for research and for staff training are briefly discussed.