BACKGROUND/OBJECTIVE: Delirium is a common clinical problem in elderly patients. We aim to investigate whether anaemia is a risk factor for delirium in a hospitalized geriatric population. METHODS: During a 5-month prospective study, we investigated 190 elderly patients aged 70 years and older with a baseline Mini-Mental State Examination (short version), Confusion Assessment Method, demographic, clinical and laboratory data. RESULTS: Thirty-four patients were identified as delirious and 95 as anaemic according to the WHO criteria. Stepwise logistic regression revealed that anaemia (haemoglobin level <12 g/l in women and <13 g/l in men), male sex and a diagnosis of dementia were independent risk factors for delirium in the total study group. After adjustment for sex, age, diagnosis of dementia and dehydration, the odds ratio (OR) for anaemia (2.4; 95 CI = 1.02-5.54) remained significantly associated with delirium. When the study population was classified in groups according to sex, anaemia remained a significant risk factor for delirium in men (OR = 3.7; 95% CI = 1.03-15.6) after adjustment for the multiple variables but not in women (OR = 1.54; 95% CI = 0.48-4.9). When the haemoglobin levels were stratified into sex-specific quartiles, the adjusted OR for delirium for men with a haemoglobin level less than 11.1 g/dl was 13.1 (95% CI = 1.17-146). CONCLUSION: Anaemia is an independent risk factor for delirium and adds valuable information to previously validated predictive models in men but not in women and lower haemoglobin levels were associated with higher risk levels.