Abstract The computer has significantly influenced the practice of educational testing, by permitting more thorough evaluation of test results and by facilitating the compilation of large banks of validated test items. However, the computer is often passive, rarely taking part in the testing, merely processing results to provide information for diagnosis, assessment and decision-making. While objective test items are finding an increasing use in the assessment of factual knowledge, it is less widely appreciated that they can be used in a teaching-learning context. The computer-controlled presentation of such items with associated correct answer(s) and an explanation can pin-point inadequacies and inaccuracies in the factual knowledge of each student and provide immediate correction on an individual basis, allowing the student to eliminate errors and manage his learning more appropriately. A system is described which presents objective test items to students, checks their answers and gives explanations. Mention is also made of GALTS, of which it forms part, and the technique of selecting and sequencing computer-based modules by means of an independent control program. Details of the use of the system by first year pharmacology students and an analysis of the results of an examination at the end of the year are presented.