Muscular adaptation to physical exercise has previously been described as a repair process following tissue damage. Recently evidence has been published to question this hypothesis. The purpose of this study was to investigate inflammatory processes in human skeletal muscle and epimysium after acute physical exercise with large eccentric components. Three groups of subjects (n = 19) performed 45 min treadmill running at either 4 degree (n = 5) or 8 degree (n = 9) downhill or 4 degree uphill (n = 5) and one group served as control (n = 9). One biopsy was taken from each subject 48 h post exercise. Blood samples were taken up to 7 days post exercise. Compared to the control group, no marker of inflammation in muscle and epimysium samples was different in any exercised group. Only subjects in the Downhill groups experienced delayed onset of muscle soreness (DOMS) and increased serum creatin kinase activity (CK). The detected amount of immunohistochemical markers for T cells (CD3), granulocytes (CD11b), leukemia inhibitory factor (LIF) and hypoxia-inducible factor 1b (HIF-1b) was greater in epimysium from exercised subjects with DOMS rating of >3 (0-10 scale) but not higher than controls. Eccentric physical exercise (downhill running) did not result in skeletal muscle inflammation 48 h post exercise, despite DOMS and increased CK. It is suggested that exercise can induce DOMS by activating inflammatory factors present in epimysium before exercise. Repeated physical training may alter epimysium content of inflammatory factors and thus reduce DOMS.