In psychology, the term intelligence has been introduced for the description of the certain, theoretically postulated complex of psychical events (thinking, attention, imagination, memory etc.). Intelligence belongs to the category of personality features, to its attributes. It has certain structure, which has been shown from the viewpoint of ontogeny, to be dynamical during the development of the individual. Intelligence testing belongs to one of the oldest psychodiagnostic methods used to measure not only ones mental abilities, but also the current individual mental level. This is the reason why careful interpretation of its results is always so crucial. Mentioned are examples of some of these tests, its interpretation, quality and proficiency. Discussed are also questions of the diagnostic usefulness of these tests.