University students often report high stress levels, and studies even suggest a recent increase. However, there is a lack of theoretically based research on the structural conditions that influence students' perceived stress. The current study compared the effects of Karasek's demand-control dimensions with the influence of neuroticism to address environmental and individual characteristics related to stress. Two points of measurement were included: T1 in the middle of the term and T2 during the examination period. Participants were 146 psychology students at two German universities (M[subscript age] = 22.6 years). We applied an adapted version of Karasek's Job Content Questionnaire, a self-developed stress scale, and the 21-item Big-Five-Inventory. At T1, both neuroticism and demands significantly predicted stress (total adjusted R[superscript 2] = 0.40), although relative weights analyses indicated that the contribution of demands was more pronounced (relative importance: 63%). Longitudinally, controlling for stress at T1, the demand-control dimensions explained additional variance in the increased stress level at T2, whereas neuroticism did not contribute additionally (R[superscript 2] = 0.52). Results indicate that self-reports on stress among university students are not only a reflection of underlying negative affectivity. We conclude that perceived stress can be explained by structural conditions rather than personality, providing opportunities to reduce stress among students.