Objectives: The clinical implication for high access flow(Qa)/ cardiac output(CO) is not well known in patient with hemodialysis (HD). The purpose of this study was to analyze clinical implications by comparing the characteristics of Qa/CO at baseline and 1 year later. Methods: We performed an observational study of prevelant HD patients. Patients were divided into two groups according to Qa/CO of 0.3. We measured CO, Qa, brachial artery flow, and volume status. In addition, we analyzed and compared changes in Qa/CO and related parameters after 1 year later. Results: The number of patients with a Qa/CO value of 0.3 or higher was 27 out of 133(20.3%) patients. Qa (2.00 ±0.51 vs. 0.95±0.34 L/min, p < 0.001), diastolic blood pressure(DBP) (74.2 ±15.6 vs. 67.0±14.4 mmHg, p =0.023), end diastolic velocity (EDV) (137.0±48.2 vs. 99.8±42.1 cm/s, p < 0.001) and diameter (0.60±0.13 vs. 0.53±0.10 mm, p = 0.002) of brachial artery were higher, but CO (4.99±1.25 vs. 5.85±1.58 L/min, p = 0.01) were significantly lower than those of group with Qa/CO less than 0.3. There was a significant higher Qa/CO in patients with non-diabetes(p=0.037) and upper access(p < 0.001). In the multivariate analysis, upper access (odds ratio [OR], 3.882; 95% confidence interval [CI] 1.30111.579) DBP (OR, 1.048; 95% CI 1.0101.088), and EDV (OR, 1.020; 95% CI, 1.0081.033) were independent risk factors for high Qa/CO. The Qa decreased (2.00 ±0.51 vs. 1.66±0.63 L/min, p = 0.002) but CO (5.80±1.52 vs. 6.23±2.64 L/min, p = 0.013) increased significantly in the group with higher Qa/CO patients. Conclusions: Patients with high Qa/CO had lower CO than that of normal Qa/CO. The upper access, DBP and EDV are significant risk factors for high Qa/CO. The Qa decreased but CO increased after one year later. More research is needed to find out the clinical significance of changes in Qa and CO.