Job satisfaction can be conceptualized as a function of situational conditions, personal characteristics, and interactions between both groups of variables. The authors compared the relative predictive power of these determinants in 3 samples of professionals (total N = 1,065). Perceived job characteristics (qualification possibilities, social support, stress, autonomy, participatory leadership) uniquely explained 7-22% of the variance in job satisfaction, and dispositional factors (Big Five, occupational self-efficacy, work centrality, mastery goals) uniquely explained 8-12% of the variance. Dispositional influences were partially mediated by perceived job characteristics. Interactions between situational and dispositional factors were of little significance. The authors concluded that perceived job characteristics (especially autonomy and participatory leadership) are important determinants of job satisfaction, and neuroticism is an important determinant as well. Highly educated professionals' job satisfaction also seems to be driven by qualification possibilities.