Here we report studies in a large cohort (n = 943) of critically ill patients with SIRS in which we have simultaneously measured circulating levels of pro-inflammatory cytokines and chemokines (IL-6, IL-8, G-CSF, sTNFR-1) and markers of endothelial activation/dysregulation (Ang-1, Ang-2, sVCAM-1) in plasma obtained within 24 hours of presentation. The gene discussed is IL6; the disease is systemic inflammatory response syndrome.