The author has made up a diagnostic the statistical occurrence of signs of basis psychological key on the basis of his own shortcomings, disturbances or mental diexperience as well as that of others and senses among pupils of the 9 to 15 age -group. He verified this key oil 30 pupils with different diagnoses (15 of them being psychiatric cases), whose current anamneses were presented to first-year students of the Pedagogical Faculty on the one hand, and to teachers at the Basic Nine-Year School on the other hand. Both students and teachers had to base their answers on the signs in the anamneses and on the key. The number of correct solutions in the student group (involving .groups of 10 to 28 persons) was within the range of about 85 to 100 per cent. In the teacher group there were 81.1 per cent of correctly solved diagnoses and 8.1 per cent of partially correct solutions, which shows that the reliability of the key is relatively high. The key is made up in such a way that any possible errors can be eliminated in further process and the diagnostician can come back to the right track. The author then further suggests a simple principle of computer diagnostics by means of punch cards and using the elimination method, which is substantially simpler than similar suggestions and operates with only a small number of punch cards.