The aim of this survey was to determine the prevalence of current and lifetime mental disorder and deliberate self-harm among male prisoners in Greece. The subjects were 80 randomly selected remanded and sentenced prisoners in a Greek prison. They were assessed for mental disorder including suicidality and substance misuse using the Mini International Neuropsychiatric Interview (MINI). We also collected information regarding contact with psychiatric services, previous deliberate self-harm as well as physical health and conducted a brief assessment of their intellectual functioning. Mental disorder was diagnosed in 63 (78.7%) prisoners. The main diagnoses were: anxiety disorder, 30 (37.5%); major depression, 22 (27.5%); antisocial personality disorder, 30 (37.5%); alcohol dependence, 21 (26.3%) and opiate dependence 22 (27.5%) and schizophrenic or bipolar disorder 9 (11.2%). Deliberate self-harm prior to and during imprisonment was reported by 15% and 2.5% of prisoners, respectively, and 12 prisoners (15%) had IQ below 75. This survey identified a significant level of need for specialist mental health services in prison. Further studies are required to assess the specific needs of those patients who are too unwell to remain in prison, the need for specific treatments for substance misuse and improved assessment/treatment of common psychiatric disorders.