Aim: Apelin and ADMA may have opposite impacts on the activity of NOS and production of NO. However, the circulating level and cardiovascular role of apelin are unclear in uremia patients with elevated ADMA. Our present study was to detect the serum level of apelin-13 and ADMA, and their correlations in maintenance hemodialysis (MHD) patients. Methods: 159 MHD patients without heart failure (HF) and twenty healthy volunteers were enrolled. Pre- and post-dialysis concentrations of serum apelin-13 and ADMA in MHD patients and in controls were determined. Nitrite and nitrate (NOx) were measured at the same time. The levels of apelin-13, ADMA, and NOx in dialysate or ultrafiltrate were tested, and the total removal (TR) of them in 1 session were calculated. It was also analyzed for the correlations among apelin-13, ADMA, NOx, apelin/ADMA ratio and other clinical parameters, such as blood pressure, urea reduction rate (URR), and so on. Results: The serum levels of apelin-13 and ADMA in MHD patients were both higher than healthy controls (104.63 +/- 40.35 ng/ml versus 55.57 +/- 21.06 ng/ml, p = 0.016; 1.05 +/- 0.67 mu M vs. 0.35 +/- 0.06 mu M, p = 0.002, respectively). There was no significant difference in serum NOx levels between MHD patients and healthy controls (58.30 +/- 40.09 mu M vs. 68.11 +/- 13.63 mu M, p = 0.596). Except for the significantly increased NOx (from 58.30 +/- 40.09 mu M to 96.14 +/- 58.07 mu M, p < 0.001), the serum levels of apelin-13 (from 104.63 +/- 40.35 ng/ml to 76.44 +/- 40.47 ng/ml, p = 0.012) and ADMA (from 1.05 +/- 0.67 mu M to 0.83 +/- 0.53 mu M, p < 0.001) decreased significantly after hemodialysis session. Apelin-13, ADMA, and NOx all can be removed by HD. The pre-dialysis serum level of apelin-13 was positively correlated with the one of ADMA (r = 0.349, p = 0.001) and LDL (r = 0.204, p = 0.041), but ADMA was positively correlated with SCr (r = 0.277, p = 0.027). There were negative relationships between serum levels of ADMA and NOx for both pre- and post-dialysis (r = -0.344, p = 0.047, and r = -0.612, p = 0.001, respectively). The apelin/ADMA ratio had significantly negative correlations with systolic blood pressure (SBP) (for predialysis, r = -0.277, p = 0.037, for post-dialysis r = -0.754, p = 0.019, respectively). Conclusion: The serum concentrations of both ADMA and apelin-13 are increased in MHD patients without HF, and there were positive correlations between them predialysis. Both of them might affect patients blood pressure.