Currently, the mood states are regarded as monopolar. This study tested in psychiatric subjects for the presence of five bipolar mood states after the influence of extreme response bias had been removed. The affective states hypothesized were: composed vs anxious, agreeable vs hostile, energetic vs fatigued, elated vs depressed, and clear-thinking vs confused. The sample of 303 cases included anxious, depressed and agoraphobic cases. Ratings of the 72 adjectives of the Profile of Mood States were intercorrelated. After extreme response bias score was partialled out the resulting correlations were analyzed by the method of principal components. The five factors isolated clearly support the bipolar nature of mood states postulated.