In this study, factors related to reversibility and mortality in consecutive cases of Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) delirium [n = 121] occurring in palliative care patients were evaluated. Delirium was assessed with the revised Delirium Rating Scale (DRS-R98) and Cognitive Test for Delirium (CTD). Patients were followed until recovery from delirium or death. In all, 33 patients (27%) recovered from delirium before death. Mean time until death was 39.7 +/- 69.8 days in patients with reversible delirium [n = 33] versus 16.8 +/- 10.0 days in those with irreversible delirium [n = 88; P < 0.01]. DRS-R98 and CTD scores were higher in irreversible delirium (P < 0.001) with greater disturbances of sleep, language, long-term memory, attention, vigilance and visuospatial ability. Irreversible delirium was associated with greater disturbance of CTD attention and higher DRS-R98 visuospatial function. Survival time was predicted by CTD score (P < 0.001), age (P = 0.01) and organ failure (P = 0.01). Delirium was not necessarily a harbinger of imminent death. Less reversible delirium involved greater impairment of attention, vigilance and visuospatial function. Survival time is related to age, severity of cognitive impairment and evidence of organ failure.