Models based on modern theories of anxiety were used to develop a hypothesis concerned with the relationship of anxiety and/or the tendency to aggressive behavior and the tendency to depressive reactions in prisoners. Anxiety, aggression and depression scales were the instruments used in this study. Special emphasis was placed on the question as to whether there is a quantitative difference in anxiety and aggression in non-working as compared with working prisoners. Significant differences were found between working and non-working prisoners with regard to anxiety and depression. A difference was also calculated for the parameter of reactive aggression. In the following the far-reaching implications of these results for penological practice and perspectives for further studies are discussed.