Background:To date, most research on aggression in mental disorders focused on active-aggressive behavior and found self-directed and other-directed active aggression to be a symptom and risk-factor of psychopathology. On the other hand, passive-aggressive behavior has been investigated less frequently and only in research on psychodynamic defense mechanisms, personality disorders, and dysfunctional self-control processes. This small number of studies primarily reflects a lack of a reliable and valid clinical assessment of passive-aggressive behavior. To address this gap, we developed the Test of (...) Passive Aggression (TPA), a 24-item self-rating scale for the assessment of self-directed and other-directed passive-aggressive behavior.Method:Study 1 examined the internal consistency and factorial validity of the TPA in an inpatient sample (N= 307). Study 2 investigated the retest-reliability, internal consistency, and construct validity (active aggression, personality traits, impulsivity) of the TPA in a student sample (N= 180).Results:In line with our hypothesis, Exploratory Structural Equation Modeling revealed an acceptable to good fit of a bi-factorial structure of the TPA (Chi-square-df-ratio= 1.98;RMSR= 0.05, fit.off = 0.96). Both TPA scales showed good to excellent internal consistency (α= 0.83–0.90) and 4-week retest-reliability (rtt= 0.86). Correlations with well-established aggression scales, measures of personality, and impulsivity support discriminant and convergent validity of the TPA.Conclusions:The TPA is a reliable and valid instrument for the assessment of self-directed and other-directed passive-aggressive behavior. (shrink)