BackgroundDrug abuse is a disorder associated with unhealthy pattern of drug consumption and is a widespread social delinquent both in society and at home. There have only been a few studies conducted on the frequency and types of harmful behaviors among drug abusers.ObjectivesThe objective of this study is to investigate the frequency of harmful behaviors in people who are suffering from drug abuse.Patients and MethodsThe population was comprised of all the patients with drug abuse disorders hospitalized during 6 month from 1389 - 1390 in adult wards of Ibn - Sina Psychiatric Hospital in Mashhad. Of those patients who had been identified as having drug abuse disorder, based on the initial interview by a psychiatrist and a urine drug screening test, 99 subjects were selected as the available sample and were informed of the study and its objectives. In this descriptive study patient’s consent had been taken. In psychotic cases, legitimate guardian consent has been obtained. Furthermore, demographic questionnaire in order to determine the harmful behaviors has been completed. Comorbid psychiatric diagnosis was recorded by a psychiatrist, according to the patients’ records. SPSS software was used to analyze the results and, descriptive statistics such as frequency tables and inferential statistics including the chi-square test were used.Results85 drug abusers (58.5%) have a history of harmful behaviors and 14 persons (14.1%) have not acted out in this manner. Seventy individuals had participated in more than one harmful behavior. The most common harmful behavior has been reported as aggression by force and attack (65.5 %.).ConclusionsThe most common type of harmful behaviors was “aggression by force and attack”. The next most harmful behavior was defined as the threat of suicide. Clearly, drug abuse was a disorder strongly associated with harmful behaviors.