Although there is some evidence that duration of untreated psychosis (DUP) is geographically stable, few have examined whether the phenomenon is temporally stable. We examined DUP in two cohorts within two discrete time periods (1995-1999 and 2003-2005) spanning a decade in the same geographically defined community psychiatric service with no early intervention programme. Patients were diagnosed by Structured Clinical Interview for DSM (SCID) and we determined the DUP using the Beiser Scale. The DUP of the 240 participants did not differ significantly between study periods.