In this article the author reports on a research investigating the didactic effectiveness of the drawing as one of the traditional media of instruction. The starting point of Professor Prokič’s research was the hypothesis that the correct use of conventional aids of instruction facilitates a better understanding of abstract relationships in teaching and helps the pupils to eliminate the verbal form of instruction; further, he investigated the way in which the medium of instruction he had chosen — the drawing — affects the permanency of the knowledge acquired and the retention of the subject-matter in question. After giving theoretical reasons for the significance of the problem inquired into, the author deals with the aim, the organization, the methods, and the results of the research. The schoolchildren selected for the experimental work were pupils attending the 6th forms) of the Basic School, which can be characterized as requiring the pupils to switch over from concrete thinking to abstract thinking, and this often causes difficulties to the pupils. The experiment with parallel groups was organized at seven schools in three different environments. The subject matter chosen for the research work was a certain section of physical geography. The experimental classes used special drawings and charts in their lessons, whereas the control classes worked without them. Before the beginning of the experiment, which lasted three months, as well as after its termination, the author carried out thorough examinations by means of a number of tests which showed beyond any doubt, on the basis of statistical evidence, that the experimental group was substantially better than the control group, both in mastering the subject-matter and understanding abstract relationships. After a certain time after the termination of the experiment there were further tests with the aim of finding out the permanency of knowledge acquired by the experimental group compared with the control group of pupils, and the capability of transfer. Here, too, the use of drawings in explaining a certain section of the subject-matter proved to con tribute not only to a better understanding of it, but also to making the knowledge of it permanent and general. The author supports the extract from his extensive research work by a number of facts and illustrative examples.