We investigated the incidence and clinical characteristics associated with the use of aliases within a population attending a psychiatric unit over a 12-year period. The use of aliases was uncommonly recognised (0.7%). Alias users tended to be young. Many were non-nationals (43%). Identification usually occurred early in the admission and was often by self-admission (37%). A broad range of underlying diagnoses were noted with schizophrenia (31 %) and factitious disorder (22%) most common. A previous psychiatric (85%) or forensic history (30%) was frequently noted. Recurrence was noted in one third of cases and was significantly associated with a diagnosis of factitious disorder.