Oxidative damage and immune-inflammatory activation have been suggested to play a role in depression. The purpose of the study was to investigate possible associations and interactions of these pathophysiological mechanisms in geriatric depression by determining the levels of plasma 8-iso-prostaglandin F(2alpha) (8-iso-PGF(2alpha)) and interleukin-6 (IL-6) in elderly depressed individuals. Subjects over 60 years of age with depression and controls were randomly selected from a population in the community after screening with the Geriatric Depression Scale. Plasma concentrations of 8-iso-PGF2alpha and IL-6 were measured in both groups. Depressed patients had significantly higher mean (+/-S.D.) 8-iso-PGF2alpha levels compared to healthy controls (245.01+/-179.92 pg/ml vs 97.64+/-42.72 pg/ml, respectively). Similarly, the same groups demonstrated significantly elevated IL-6 levels compared with controls (58.73+/-39.90 pg/ml vs 15.41+/-9.27 pg/ml). This study indicates an association between increased levels of plasma 8-iso-PGF2alpha and IL-6 with depressive symptomatology in elderly individuals and indicates the necessity for further investigation, possibly within the framework of an integrated involvement of oxidative damage and inflammation in the pathophysiology of depression in the elderly.