Abstract Objective The aim of this study was to assess the possible predisposing aetiologic and short-term precipitating factors for delirium in acutely ill hospital patients with a heavy burden of comorbidities and medications. Methods Eighty-seven consecutive patients with acute delirium admitted to a general medicine unit were thoroughly examined, and the predisposing and precipitating factors of their delirium were assessed. Results In this population, an average of 5.2 predisposing factors and 3.0 potential precipitating factors for delirium was revealed, meaning an average of over eight possible aetiological causes for each patient. The most common precipitating factors were infections ( n =72), metabolic abnormalities ( n =52), adverse drug effects ( n =41), and cardiovascular events ( n =38). In addition, a number of very rare conditions were diagnosed after thorough assessments. Conclusion Geriatric patients with acute delirium typically present with several concomitant predisposing factors for delirium exposing them to high vulnerability for the syndrome. In most patients, a number of possible etiological causes for delirium can be identified after a careful assessment, but their true pathogenetic pathway to the syndrome is unclear.