Background/Aims: Temperament and mood swings are promising indicators for the characterization of mood spectrum vulnerability. The aim of this study was to investigate the relationship between affective temperament and mood swings in bipolar disorder. We explored these clinical features retrospectively. Methods: Patients who met the criteria for bipolar I disorder were enrolled in the study. Exclusion criteria were partial remittance and a full affective or psychotic episode. Data concerning illness and family history, mood swings (semistructured interview for mood swings) and depression (Beck, Depression Inventory) were obtained. We examined premorbid temperament with the validated German version Temps-M of the original version Temps-A. Patients with and without mood swings were compared with respect to the dominant temperament. Results: Out of 20 bipolar patients, 6 subjects reported mood swings prior to the onset of affective disorder. Subjects with mood swings prior to the onset of bipolar disorder significantly correlated with a positive family history of affective disorders. Concerning cyclothymic and irritable temperament, bipolar affective patients with mood swings had higher scores. No differences were found between males and females. Conclusion: Our findings go in line with previous results that mood swings, as represented by the cyclothymic temperament, are present prior to the first onset of bipolar disorder in a subset of patients. These traits may represent vulnerability markers and could presumably be used to identify individuals at high risk for developing bipolar disorder in order to prevent this illness. Further studies are indicated to clarify the correlation with genetic risk factors.