This master’s thesis on Stress and causes of stress deals with the concept of stress and difference between positive and negative stress, describes most common causes for and sources of stress, suggests solutions to manage, relieve and even eliminate harmful effects of stress which make great damage to physical and mental health of employees and consequently cause harm to the employer since the employee can’t do all the work the employer expects him/her to do. The study is based on a research conducted on 45 subjects aged between 20 and 66 years, with the majority in their early and mid-twenties. Condition for participation was previous work experience. This study examined personal impressions about definition of stress, its intensity and impact on work efficiency, about sources of stress and side effects perceived when under stress, and, in the end, about ways to relief stress. Thesis introduction defines concept of stress through variety of sources, although stress itself is an individual experience, meaning that experience of stress differentiates and manifests itself differently from person to person. Second part explains survey methodology in detail, while third part deals with obtained results. A discussion section illustrates some interesting information about most stressful professions and healthy work environment, as well as consequences of stress and ways of stress relief. The conclusion will consolidate most important thesis elements.