To see if the inflammatory responses during and after laparoscopic and open inguinal hernia repairs differed. Randomised prospective study. County hospital, Denmark. 18 men aged 25-77 years with unilateral inguinal hernias. Ten patients had a laparoscopic repair and 8 an open tension-free repair. Serum concentrations of interleukin (IL)-2 receptors (R) of the alpha group (IL-2Ralpha), IL-6, anti-IL-6, IL-10, tumour necrosis factor (TNF)-alpha, sTNF-RI and sTNF-RII before and 2, 6, 12, and 24 hours after the repairs. Duration of operation and time for return to normal activities or work were also recorded. Serum IL-6 concentrations increased significantly after operation in both groups (p < 0.0001), but the increase was significantly higher after open than after laparoscopic surgery at all sampling times (p = 0.00) at 6 hours postoperatively). Anti-IL-6 and IL-10 remained undetectable at all time points. There were no significant differences or increases in the concentrations of TNF-alpha or sTNF-RII. However, sTNF-RI concentrations increased significantly in both groups (p < 0.001) though there was no difference in between the two groups. IL-2Ralpha decreased significantly in both groups (p < 0.01) with no differences between the groups. The median operation time was 85 min (range 55-100 min) in the laparoscopic group and 52 min (range 45-79 min) in the "open" group (p < 0.01). Median time to return to normal activities/work were 2 and 13 days after laparoscopic and open operations, respectively (p < 0.01). The surgical trauma of laparoscopic inguinal hernia repair is less than that of open tension-free hernia operations as assessed by circulating mediators of the postoperative inflammatory response. The clinical relevance of this finding must be evaluated in larger randomised studies.