Some people think that personality tests are very interesting, other that they are horrible. The farmer trust in personality tests, the latter refuse them at all. Measurement of characteristics that are so difficult to define (such as personality traits) can appear both possible and aberrant. The arti-cle aims at showing, in the most comprehensible way, how it is possible to measure, in a valid and reliable manner, personality characteristics. This can be done through the use of an appropriate tool which has the right psy-chometric properties.