Acts of self-harm are alarmingly prevalent. These encompass direct aggression toward one's body and indirect forms of self-harm. Evidence indicates that different types of self-harm behavior frequently co-occur. This suggests certain risk factors may act transdiagnostically across multiple forms of self-harm. Identifying these factors could enhance prevention and early intervention efforts for several behaviors simultaneously. This study aims to examine self-criticism as a transdiagnostic factor for two self-harm behaviors common among older adolescents and young adults: non-suicidal self-injury (NSSI) and disordered eating (DE). NSSI is the intentional destruction of body tissue absent the intent to die. DE refers to behaviors such as food restriction, purging, and binge eating. Both NSSI and DE are associated with heightened self-criticism, suggesting that self-criticism could be part of a transdiagnostic risk process. The precise role that self-criticism plays in the etioloy of these behaviors remains unclear, however. One possibility is that trait-like global self- criticism directly increases risk for self-harm. Alternatively, reactive self-criticism experiencedin the context of negative affect may be the more important driver of these behaviors. The study examines the relation of both forms of self-criticism to self-harm via three main aims. Aim 1 examines global self-criticism as a longitudinal predictor of both NSSI and DE. Aim 2 examines the role of reactive self-criticism. Aim 3 compares the significance of global versus reactive self criticism in relation to NSSI and DE. The study has two components. Both focus on a university-based sample of older adolescents and young adults (ages 18-25), and both utilize computer-based performance measures as well as self-report measures to enhance construct validity. Part one is a longitudinal study that prospectively examines the role of self- criticism in the development of NSSI and DE. Part two is a laboratory-based study that will examine the role of reactive self-criticism by assessing self-criticism in the context of a negative mood induction. The ultimate research goal is to identify common factors leading to multiple forms of self-harm, thus enhancing prevention and early intervention efforts for these pernicious behaviors. Training tied to the proposal will enhance skills in assessment (e.g., clinical interview methods and information-processing measures), advanced data analysis (e.g., regression and structural equation modeling), and scientific professionalism (e.g., publication preparation and grant management). Together, the research and associated training lay the groundwork for a productive career as a clinical investigator of self-harm behaviors.