['To determine whether the main mitochondrial DNA (mtDNA) haplogroups of the Han people have an impact on long-term clinical outcome.', 'We prospectively studied 181 individuals who were sequentially admitted to the intensive care unit. Demographic and clinical data were recorded along with clinical outcome over 180 days. Follow-up was completed for all study participants. We then determined the mtDNA haplogroups of the patients and 570 healthy, age-matched Han people from Zhejiang province, Southeast China, by analyzing sequences of hypervariable mtDNA segments and testing diagnostic polymorphisms in the mtDNA coding region with DNA probes.', 'The frequency of the main subhaplogroups of the Han population in the study cohort did not differ significantly from the control group. mtDNA haplogroup R, one of the three main mtDNA haplogroups of the Han people, was a strong independent predictor for the outcome of severe sepsis, conferring a 4.68-fold (95% CI 1.903-10.844, P = 0.001) increased chance of survival at 180 days compared with those without the haplogroup R.'] Does mitochondrial DNA haplogroup R predict survival advantage in severe sepsis in the Han population?