The aim of this study was to examine predisposing and precipitating factors of acute confusional state (ACS) retrospectively in medical records of patents examined in an acute medical unit (AMU) who had a preliminary diagnosis of confusion/anxiety. The study comprised all 221 patients who were 65 years old and older among the 18,015 patients examined in the AMU during 1 year who, after a preliminary examination in the AMU, received a diagnosis of confusion/anxiety without any other etiologic diagnosis. Fifty-six cases fulfilled the DSM-III-R criteria for ACS. The control group comprised 165 patients, with anxiety, depression, or psychosis the main finding in 135 cases. Among patients further examined in other departments or for whom consultations were made, the medical records showed that the ACS group had on average 2.6 predisposing factors for ACS, with dementia, cerebrovascular disease, and sensory deficits the most common. Three to six predisposing factors were found among 46% of the ACS patients, compared to 4% of the control group. A precipitating factor of ACS was found in 78% of the ACS cases, and the average number of precipitating factors was 1.6. Dementia (32%), metabolic disturbances (30%), and cardiovascular diseases (16%) were the most frequent precipitating factors among the ACS group. The mortality rates 2 years after examination in the AMU were 32% for the ACS group and 20% for the control group (p < .05). The study suggests that the causes of ACS are often multifactorial and that it is important to seek several precipatating factors when treating this potentially reversible condition.