The author argues that tests should be used only by professionals knowledgeable in the theory and methodology of psychodiagnostics, familiar with the range of various techniques, and experienced in interpreting test results and applying them to practice. By contrast, a non-professional interpretation of test results raises unjustified expectations and doubts in the usefulness of testing. The author examines whether intelligence tests measure general intelligence or some particular aspects of cognition. She discusses some practical tasks for which intelligence tests can be useful.