A systematic review is devoted to epidemiology of adverse events in short-stay hospitals in foreign countries. It is found that dualism is an important feature of medical care, since treatment results can be not only useful, but also harmful (adverse events) associated with medical care per se. Adverse events are diagnosed in 10.68% of patients. Moreover, complications occur at previous stages of treatment in 20.91% of cases. Incidence of adverse events is 2 times higher in surgical departments and intensive care units compared to therapeutic departments. Among all adverse events, 42.83% are associated with open surgery, 16.17% with drug therapy, and 14.10% with manipulations or minimally invasive interventions. Preventable adverse events caused by human factor account for 48.24%. In other cases, adverse events are the result of side effects of medical technologies, exposure to physical environment and unsafe patient behavior. Infection associated with medical care (28.15%) prevails among other adverse events. In 51.45% of cases, adverse events are characterized by mild harm and do not prolong hospital-stay. Moderate harm requiring additional in-hospital treatment develops in 31.80% of cases. In 11.89% of cases, adverse events are life-threatening complications and/or cause disability. Moderate-to-severe harm increases hospital-stay by 8.7 days. Incidence of adverse events followed by unfavorable outcomes is 5.25%. Overall mortality and mortality from adverse events are 6.67% and 0.55%, respectively. Deaths associated with adverse events account for one in five deaths in a hospital and one in ten deaths in population of developed countries.