The current study investigated over time variation of Positive and Negative Affect and the relation between mood level and personality characteristics. 68 male undergraduate volunteers completed the Multidimensional Personality Questionnaire and then recorded mood ratings daily over a 29-day period. Spectra time series analyses showed a distinct and significant seven-day cycle for Positive Affect and Negative Affect, with the peak in Negative Affect occurring approximately three days after that of Positive Affect. Positive Affect was significantly correlated with scores on Well-being, Social Closeness, Social Potency, and Absorption scales of the questionnaire, while Negative Affect was significantly related to scores on the Stress-Reaction, Alienation, and Aggression scales.