Acting and acting pathologies: how to articulate these two concepts that often refer to each other, like an echo that can be difficult to discard? Do all types of acting out reflect a form of psychopathology and hence create the risk of confusion between transgression and mental illness? Is acting out necessarily an "out-law" of psychic life? The aim of this text is to try to broaden the implications related to these interrogations with the use of projective tests. The first section will treat the different ways in which acting out participates in psychic life and how projective tests are a privilaged form of observation allowing to determine the singularity of the role of acting out in psychic functioning. The second section will propose clinical examples of acting out pathologies during childhood and adolescence