Objective: Knowledge about the characteristics of patients using psychiatric emergency services is expanding. However, the prevalence of HIV infection among patients treated at psychiatric emergency departments is not known, and neither are the characteristics of HIV-positive patients seen in this setting.Methods: To estimate the prevalence and demographic and clinical correlates of HIV infection among patients utilizing psychiatric emergency services in a level 1 trauma center, the authors analyzed data from a series of 58,301 consecutive visits (28,817 unique patients).Results: Of the total psychiatric emergency visits, 2.0% were by HIV-positive patients, who were more likely to be male, homeless, or African American. These patients were also more likely to show dementia or to be suicidal, abusing substances, or coping with borderline personality disorder.Conclusions: More precise description of HIV-positive patients visiting psychiatric emergency departments may help elucidate the needs of this population and help plan for improvements in care in this setting.