Purpose: The aim of the present cross-sectional study was to explore which variables could explain the perceived exertion during a graded exercise test (GXT) in patients with depressive and anxiety disorders. Method: In three treatment units of a university psychiatric hospital in Belgium, 137 patients (49 males and 88 females) performed a submaximal GXT the first week of admission. The rate of perceived exertion (RPE) at 60% of the maximal heart rate reserve (MHRR) was measured by means of the Borg Category Ratio 10 Scale. Depression, anxiety, level of physical activity and perceived cardio-respiratory fitness were evaluated by means of questionnaires. The motivation towards exercise therapy was measured using a visual analogue scale. A linear multiple regression equation was used to ascertain the explaining variables for the perceived exertion. Results: The explaining variables for RPE at 60% of MHRR, in order of importance, were age, level of physical activity and state anxiety. Conclusions: Patients who are older, less active and/or patients with a high anxiety level perceive a high RPE during a GXT. These findings should be taken into account in the use of exercise tests and exercise prescriptions for depressed and anxious psychiatric patients. [ABSTRACT FROM AUTHOR]