This study explored the symptoms of self-injurious behaviour (SIB) in a consecutive sample of 54 mostly female psychiatric inpatients. The phenomenological analysis presented SIB as quite a uniform syndrome that starts latest in early adulthood, is often committed impulsively, is used in the function of releasing tension and occurs in patients with eating and psychoactive substance use but also schizophrenic disorders. The quality of mood preceding SIB was best characterized as dysphoria and was qualitatively not different from patients' longstanding affective traits. Two subgroups were differentiated, those with borderline personality disorder and those without; there was some evidence that patients with borderline personality disorder present a quite homogeneous core group of SIB, whereas others show a higher variety of psychopathological features. The hypothesis is proposed that poor affect regulation is the underlying psychopathological dimension.