['To assess the serum levels of interleukin 1beta (IL-1beta) in elderly depressed patients in comparison with nondepressed healthy elderly subjects.', 'Cross-sectional study.', 'Tertiary memory clinic.', 'Twenty-three antidepressant-free elderly depressed patients and 44 nondepressed healthy elderly comparison group were enrolled to this study.', 'Serum IL-1beta levels were determined with highly sensitive colorimetric sandwich enzyme-linked immunosorbent assay. Severity of the depressive episode was determined by scores on the Hamilton Depression Scale-21 item and cognitive performance by the scores on the Cambridge Cognition Examination, Mini Mental State Examination clock drawing test, and verbal fluency.', 'IL-1beta serum levels were increased in elderly patients versus nondepressed elderly (t = 2.21, df = 65, p = 0.04). After categorizing elderly depressed subjects into late onset (LOD) versus early onset (EOD), patients with EOD had the highest IL-1beta levels, when compared with nondepressed elderly patients and patients with LOD in analysis of variance (F = 4.9, df = 2, 64, p <0.01).'] Is interleukin-1beta serum levels increased in antidepressant-free elderly depressed patients?