Our objective was to investigate the initiation and course of pro- and anti-inflammatory cytokines in early inflammatory response and to elucidate the cytokine system in relation to the adrenal response caused by stress. Seven blood samples were collected, pre- and postoperatively (0-72 h) after total hip replacement (THR) due to osteoarthritis. The following cytokines were measured using Cytometric Bead Array: interleukin-1beta (IL-1beta), IL-6, tumour necrosis factor-alpha, IL-8, IL-12 and IL-10 (B&D). Thirteen patients took part in the study (67 +/- 9 years). C-reactive protein increased from <6 to over 200 mg/l on the second post-op day. The concentration of IL-6 increased 10-fold just 3 h post-op (4-47 pg/ml) and reached its maximum value 6 h post-op (77 pg/ml; Wilcoxon test P < 0.01) Repeated measurements were also significant (Friedman P < 0.05). The concentration of IL-8 doubled the day of surgery but did not reach a significant level (Friedman test =0.069). None of the other cytokines showed any significant changes. The diurnal cortisol rhythm was interrupted after the surgery and there was a significant correlation between the cortisol secretion and IL-6 response. This study demonstrates an isolated elevation in IL-6 levels with only a minor elevation in IL-8 following THR. This pro-inflammatory response seemed to decline without activation of anti-inflammatory cytokines (IL-10), but cortisol seemed to play a complicated role in halting the acute inflammatory response.