In temperament research, three traditions can be found: (1) in psychiatry or psychopathology, (2) in neurobiology, and (3) in developmental psychology. After giving an overview, we present results and theories concerning the relation between temperament and affective disorders. Based on Kraepelin's concept of the fundamental states ("Grundszustände"), we describe four types of temperament: hyperthymic (manic), depressive, irritable, and cyclothymic. A fifth anxious temperament is added. Clinical description and scientific implications are described in the light of recent work by Akiskal and the German version of the TEMPS-A scale, a self-report questionnaire for assessing temperament.