The aim of this research was to estimate the psychiatric service requirements for the remand population. We interviewed 232 (42.6%) men, a rep-resentative sample of men on remand, using the SADS-L, SODQ and a structured demographic interview. We found high rates of psychiatric morbidity in our sample. The six month prevalence of psychosis was 7.6%, almost twice the rate in a recent international meta-analysis. Major depressive disorder was present in 10.1% (six month prevalence). Substance misuse problems were also common but there was no significant difference between rates of substance misuse in psychotic and non-psychotic prisoners. A total of 31.2% had a lifetime history of any mental illness (excluding substance misuse, adjustment disorder and personality disorder). The high levels of psychiatric morbidity detected in our sample indicate a substantial unmet need for mental health services and addiction treatment services for the mentally ill in Irish prisons.