Overdose is a serious problem as for people addicted to opioid drug injections (ODI) as well as for the community in general. To study characteristics of overdose, authors examined 60 ODI users and analyzed 27 overdose death cases. It has been shown that overdose is rather common among ODI users. Fatal and nonfatal overdoses most frequently take place among men at home or in the street. People often did not receive sufficient help in the overdose situation. We confirm the role of alcohol, long abstinence and variability in drug quality in the development of overdose. Witnesses of overdose in other users reported more health problems, family and social relations, were more concerned with their own and others risk in future compared to those reporting no overdose. Additional predictors were determined: a higher number of overdoses in the past; disturbances of family relations and somatic disorders. Mental disorders predicted the opioid overdose risk among ODI users. ODI users are interested in counseling and training to prevent overdose. Family psychotherapy and early diagnosis of comorbid disorders may be important ways of overdose prevention.