The author publishes the results of the first pedagogical experiment with problem instruction in technical subjects at secondary schools in Czechoslovakia. He accounts for the need to introduce problem instruction into classroom practice and gives its characteristics in brief The main objective of the research was to compare the effectiveness of problem instruction with that of traditonal (informative — receptivje) teaching. The criteria of effectiveness were the following: pupils’ memory perfomance, transfer, pupils’ attitude to the teaching process, speed in solving assignments, speed and success in the acquisition of knowledge and skills by pupils. The author used 7 research methods, the principal of which was the natural pedagogical experiment. The experiment was carried out at a senior technical high school (engineering) in the following subjects: mechanics, technical drawing, construction and operation of machinery. The experiment was carried out for a period of four years. The total number of pupils involved in the experiment was 662. The research confirmed significantly higher effectiveness of problem instruction compared with traditional instruction in the fields of transfer, speed in solving assignments, pupils’ attitude to the teaching process as well as in the success in the acquisition of knowledge and skills pupils. Problem teaching makes it possible for a majority pupils to learn the new subject-matter in class, during the teaching periods. No statisticaly significant differences were found between the group organization of pupils’ work (problem group instruction) and individual work combined with collective work of the class (problem frontal instruction). A condition of successfull realization of problem instruction is the orientation on the basic structure of the teaching material, setting reasonable, unequivocal and controllable goals in instruction, use of general algorithms and heuristic processes, pupils’ motivation and a differentiated approach to them.