PURPOSE: The aim of the study was to investigate possible associations between different heart rate variability (HRV) indices and various biomarkers of inflammation in 45 septic patients. MATERIALS AND METHODS: We daily assessed HRV in the time domain (SD of RR intervals [SDNN]), frequency domain (low [LF], high frequency [HF], LF/HF as an indicator of sympathovagal balance); the 2 values of SD (SD1, SD2) from the Poincare plot; and measured C-reactive protein, interleukin 6, and interleukin 10 serum levels in patients with sepsis and mean Sequential Organ Failure Assessment score (SOFA) 10 or lower (n = 25) and septic shock (SOFA > 10, n = 20) for 6 days. RESULTS: C-reactive protein exhibited significant negative correlations with LF (r = -0.78), LF/HF (r = -0.61), and SDNN (r = -0.79) and positive correlations with HF (r = 0.80) and SD1/SD2 (r = 0.66), whereas interleukin 10 was positively correlated with HF (r = 0.71) and negatively with LF (r = -0.89) and LF/HF (r = -0.66) in septic shock patients (P < .05 for all comparisons). Standard deviation of RR intervals and HF proved to be independent predictors of the severity of disease (beta slope [B] = -1.091; P = .013; 95% confidence interval [CI], -1.43 to -0.74, and B = 0.78; P = .022; 95% CI, 0.21-1.35, respectively). CONCLUSIONS: Our data suggest that low HRV and sympathovagal balance during septic shock are associated with both an increased hyperinflammatory and antiinflammatory response.