Attenuation of exercise-induced interleukin-6 (IL-6) responses by carbohydrate (CHO) has been demonstrated in studies comparing controlled doses (> or = 0.9 g x kg(-1) x h(-1)) to placebo, but not in studies of voluntary intake. This study sought to determine if attenuation of the IL-6 response during a 32.2-km mountain trail race occurs for high compared to low ad libitum CHO intakes. IL-6, C-reactive protein (CRP), and creatine kinase activity (CK) were analyzed from blood samples collected 12 h pre-, 0, 4, and 24 h post-race. Subjects were grouped into low (n =14, 0.4 +/- 0.1 g x kg(-1) x h(-1)) and high (n =18, 0.8 +/- 0.2 g x kg(-1) x h(-1)) CHO intake groups. IL-6 0 h post-race (P < 0.05) was higher in the low (40.2 +/- 22.7 pg x mL(-1)) compared to the high CHO group (32.7 +/- 22.1 pg x mL(-1)). CRP and CK both increased post-race, but no differences were observed between groups. Attenuation of exercise-induced IL-6 is apparent across a range of CHO intakes.