To compare the cytokine response to exhaustive running in recreationally-active (RA) and endurance-trained (ET) men. Eleven RA men (VO 55 ± 7 mL·min·kg ) and 10 ET men (VO 68 ± 7 mL·min ·kg) followed a controlled diet and refrained from volitional exercise for 8 days. On the fourth day, participants completed 60 min of treadmill running (65 % VO), followed by intermittent running to exhaustion (70 % VO). Fasting blood was obtained at baseline, after 20, 40 and 60 min of exercise, at the end of intermittent exercise, during 2 h of recovery and on four follow-up days (FU1-FU4). Tumour necrosis factor-alpha (TNF-a), interleukin-1ß (IL-1ß), interleukin-6 (IL-6), interleukin-1 receptor antagonist (IL-1ra) and creatine kinase (CK) were measured. Exercise increased the concentrations of all cytokines and CK, but there were no significant differences between groups. IL-1ß increased (2.2-2.5-fold, P <0.001) during exercise, while TNF-a was increased (1.6-2.0-fold, P <0.001) during exercise and for 2 h post-exercise. IL-6 (71-84-fold, P <0.001) and IL-1ra (52-64-fold, P <0.001) were increased throughout exercise and up to FU1, peaking immediately after exercise and at 1.5-2 h post-exercise, respectively. CK concentrations were increased (P <0.001) throughout exercise and up to FU4, peaking at FU1, but were not associated with changes in any cytokines. Exhaustive running resulted in modest and transient increases in TNF-a and IL-1ß, and more marked and prolonged increases in IL-6 and IL-1ra, but improved training status did not affect this response. Increased CK might indicate either exercise-induced muscle cell disruption or increased cell permeability, although neither appears to have contributed to the increased cytokine concentrations. © 2013 Springer-Verlag Berlin Heidelberg.