This study explored associations of psychosocial stress at work with depressive symptoms in a group of middle-aged employees. Psychosocial stress at work was conceptualized in terms of the model of effort-reward imbalance. This model is measured by a psychometric scale containing 23 Likert-scaled items. Depressive symptoms were assessed by the German version of the CES-D scale. The sample consisted of 316 (44.6 +/- 7.5 years) men and women employed in an urban transport enterprise. Multivariate logistic regression analysis adjusting for relevant confounders indicated an odds ratio of 5.9 (95 % CI 2.4 - 14.3) for depressive symptoms among employees defined by imbalance of high effort and low reward at work. An association of similar strength was found among employees characterized by a high level of work-related over-commitment. Findings reported for the first time in Germany are in line with two international investigations.