After the Swiss Alpine Marathon in Davos (67 km, altitude difference of 2300 m) the majority of the athletes are suffering from muscle soreness. The goal of the study was therefore to investigate muscle damage, inflammatory reactions and soreness perception during and after this ultramarathon. 27 athletes took part in the study. Creatine-kinase (CK) and C-reactive protein (CRP) were measured 24 hours before the race, immediately before and after the race as well as 2 hours, 24 hours and 48 hours, after the race respectively. Muscle soreness of the lower extremities before and during stretching were assessed at the same time points using a visual analog scale from 1 to 10 (VAS). Significant CK elevations were found in all runners ranging from 600 to 28,000 U/l. Compared to the values before and 48 hours after the start all athletes showed 24 hours after the start significantly elevated CRP values, indicating a pronounced systemic inflammatory reaction. Immediately after the race all runners reported a significantly elevated muscle soreness with maximal pain in the posterior muscles of the lower leg. In order to assess the influence of a nonsteroidal antiinflammatory agent on muscle damage, muscle soreness and inflammatory reactions 16 of the 27 runners received *Diclofenac SR. We were unable to find a difference in the mean plasma CK and CRP activity after the race between both groups, but there was a highly significant, till now to our knowledge never described correlation between the degree of muscle damage and systemic inflammatory reaction (r = 0.75, p < 0.02) in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)