Background Endogenous hydrogen sulfide (H2S) plays an important role in hypertension.The aim of this study was to investigate the role of erythrocyte and serum H2S in patients with untreated essential hypertension.Methods We recruited 62 patients (age 22-74 years) with untreated prehypertension or hypertension,and 64 normotensive subjects (age 18-64 years).We assessed the 3-mercaptopyruvate sulphurtransferase (MPST) protein expression in erythrocytes and measured the H2S production from erythrocytes and serum H2S levels,then analyzed the association of erythrocytic or serum H2S content and blood pressure or cardiovascular risk factors (e.g.,age,body mass index (BMI) and dyslipidemia).A stepwise regression analysis was used to evaluate the possible relationship of erythrocytic H2S in hypertension.Results In hypertensive patients,erythrocyte H2S production ((111.04+29.20) nmol/min per 108 erythrocytes) was higher than that in controls ((78.85±19.38) nmol/min per 108 erythrocytes),and serum H2S was also higher.The erythrocytic H2S production was associated with increased systolic blood pressure (sBP),diastolic blood pressure (dBP),age,BMI,level of C-reactive protein (CRP),as well as triglycerides (TG) and high density lipoprotein cholesterol (HDL-C).Serum H2S was not associated with age or CRP.Stepwise regression analysis showed that erythrocytic H2S production was correlated with sBP,TG,HDL-C,low density lipoprotein cholesterol (LDL-C) and blood urea nitrogen (BUN) and serum H2S was correlated with dBP and TG.Results of receiver-operating characteristic curve analysis suggested that erythrocytic H2S production was a more sensitive predictor of hypertension development than serum H2S.Conclusion Erythrocytic or serum H2S production is sensitive predictor of hypertension.