Seventy elderly patients meeting the DSM-III criteria for delirium were examined during the acute stage and followed up to one year. The mean age of the patients was 75 years (range 60-88), their delirium lasted on average 20 days (range 3-81) and the psychiatric hospitalization on average 30 days (range 8-365). The most common etiologies for delirium were stroke, infections and metabolic disorders. For 57 cases (81%) a predisposing structural brain disease was found. During the index admission, the cognitive dysfunction associated with delirium ameliorated significantly (the mean +/- SD Mini-Mental State Examination score 9.7 +/- 6.6 at admission and 13.9 +/- 7.2 at discharge; P less than 0.001), but during the one-year follow-up progression of the basic central nervous system disease was seen together with declining cognition and deterioration of functions of daily living.