The purpose of this study is to investigate HN related risk behaviors among the mentally ill adults. ELISA test has been routinely applied in Bakırköy Mental State Hospital, Forensic Psychiatric Unit. In the literature the medical and ethical procedures of the serological test application are cited. Besides the patient is always informed before and after the investigation. In this study, HN related risk behaviors defined by the literature are investigated among the mentally ill adults at the forensic clinics. The risky behaviors profile of the mentally ill adults not having alcohol or/and drug abuse are compared with the risky behaviors of the patients whose disorder are primarly alcohol or/and drug abuse, Axis I. Our results showed that HN related risk behaviors were quite low among the mentally ill adults. Based on this results, it has been thought that the routine investigation of HN related risk behaviors are more important than the routine application of the serological test among the mentally ill adults.