Objective Intradialytic hypotension (IDH) is one of the common complications during hemodialysis,however its diagnostic criteria are highly controversial at present.In order to fully understand the prevalence of IDH in our center and figure out which diagnostic criteria is better for Chinese maintenance hemodialysis (MHD) patients,we choose several IDH definitions by reviewing published literatures and analyze their association with mortality.Methods The patients were recruited from Blood Purification Center of Ruijin Hospital undergoing hemodialysis during July 2012.Pre-,intra-and post-dialysis blood pressure were recorded.Patients' clinical characteristics,laboratory results and cardiac ultrasound results were collected.Based on several IDH definitions,we investigated the prevalence rate of IDH and its frequency among MHD patients.SPSS 23.0 was used to analyze data and conduct survival analysis.Results Totally 219 MHD patients underwent 16084 hemodialysis in 6 months.The prevalence rate,overall and individual frequency of IDH fluctuated between 45.21％-100.00％,4.64％-37.60％ and 0.00％-33.00％ respectively.For every IDH criteria,the patients were recruited into the group IDH(+) if they ever met the corresponding definition,otherwise the group IDH(-).Survival analysis found that IDH (the criteria of an absolute systolic blood pressure (SBP) ＜ 90 mmHg or with a decrease of SBP≥ 20 mmHg) could decrease the risk of patients' cardiovascular mortality but was not relevant to all-cause mortality.Further analysis showed these patients had better cardiac functions mainly reflecting in lower Pro-BNP (2880 ng/L vs 6909 ng/L),lower prevalence rate of left ventricular hypertrophy (52％ vs 83％) and higher left ventricular ejection fraction (65.0％ vs 62.5％) than IDH(-) patients.No correlation was found between other IDH criteria and mortality.Conclusions The prevalence rate,overall and individual IDH frequency of IDH are of high variability when diagnosed by different IDH criteria.All IDH episodes defined by our selected definitions are of no association with all-cause mortality.An absolute SBP ＜ 90 mmHg or with a decrease of SBP≥20 mmHg can decrease the risk of cardiovascular mortality due to their better cardiac function.Large scale researches should be conducted to find optimal IDH definition and explore the association of IDH and mortality.