Chronic stress is a problem of growing importance in industrialized nations as it is accompanied by several health problems. Yoga is a holistic concept which reduces perceived stress by distinct body postures, breathing techniques and meditation. As a reliable measure of the hypothalamic-pituitary-adrenal axis activity the Cortisol Awakening Response (CAR) was utilised. It describes the cortisol rise in reaction to awakening which is supposed to prepare the organism for the upcoming day and is altered in different health conditions. The CAR, psychological health variables (BDI-II, SCL-90-R, TICS, LOT-R) and cognitive functions (Stroop-Test, d2-Test, Trail-Making-Test) were measured in a group of Yoga students and a group of control participants. The design of the study does not allow for causal interpretations but the results might reflect an acute effect of Yoga training on the CAR of the following morning possibly mediated by hippocampal activity. Furthermore Yoga seems to increase optimism and the impact of optimism on the CAR and to reduce anxiety and its'' negative impact on cognitive functioning due to relaxation and decreased fear of social evaluation.