Auto-aggressive individuals have a higher likelihood of engaging in interpersonal violence, and vice versa. It is unclear, however, whether ward circumstances are involved in determining whether aggression-prone patients will engage in auto-aggressive or outwardly directed aggressive behavior. The current study focuses on the situational antecedents of self-harming behavior and outwardly directed aggression of psychiatric inpatients. Inwardly and outwardly aggressive behavior were monitored on a locked 20-bed psychiatric admissions ward for 3.5 years with the Staff Observation Aggression Scale-Revised (SOAS-R). A map of the ward was attached to each SOAS-R form, enabling staff members to specify locations of aggressive incidents. Time of onset, location, and provoking factors of auto-aggressive incidents were compared to those connected to aggression against others or objects. Of a total of 774 aggressive incidents, 154 (20%) concerned auto-aggressive behavior. Auto-aggression was significantly more prevalent during the evening (i.e., 50% compared to 32%), and reached its highest level between 8 and 9 P.M. (17% compared to 7%). The majority of self-harming acts (66%) were performed on patients' bedrooms. Outwardly directed aggression was particularly common in the day-rooms (24%), the staff office (19%), the hallways of the ward (14%), and the dining rooms (10%). Provoking factors of auto-aggressive behavior are less often of an interactional nature compared to outwardly directed aggression. The results suggest that a lack of stimulation and interaction with others increases the risk of self-injurious behavior. Practical and testable measures to prevent self-harm are proposed.