Objective: To determine whether the nurses in intensive care units are exposed to stress, which are the factors responsible for the occurrence of stress, the influence of the stress on the working capacity of the employees. Draft study: cross-sectional study Patients and Methods: Participants in the investigations regarding the nurses and technicians working in intensive care units. Data were collected through questionnaires on stress in the workplace and a questionnaire to determine the Work Ability Index. Results: The study included 86 examinees. Most of them perceived their workplace as a source of stress. Women, whose share is 84% reported bigger stress than men (mean value of the scale of stress 48,9: P=0,028). The lack of workers as a source of stress is stated by 44% of examinees, work overlod is the source of stress for 34% of questioned workers in intensive care, 24-hour responsibility for 35% of them, fear of infection for 38% of them, and the conflict with superiors is the sourceof stress for 13% of respondents. Night work is stressful for 29%, and the time limit for carrying out daily tasks is stressful for 17% 0f respondents 51% of them evaluate their ability to work well, and 34% very good. The lower the rating of working capacity in women 3,3 (interquatile range of 2,8 to 3,5; p=0,026). Bigger stress negatively correlated with the assessment of working capacity (Sppearmans correlation coeffcient (p=-0,388; p<0,001). The professional and intellectual requirements (p=-0,382; p<0,001) and shift work (p<0,001) may influence assessment of work capacity. Conclusion: The health staff working in intensive care units experience their workplace as a sourceof stress. Lack of staff, workoverload, fear of infection, 24-hour responsibility, the timelimit for carrying out daily tasks and conflict with superiors, are cited as the most imoortant stress factors. Women are more susceptible to stress than men, which adversely affects their ability to work. Profesional and intellectual demands and shift work have the greatest impact on working ability.