The aim of the present study was to estimate the influence of hemodialysis process (HD) on the signal-averaged ECG (SAECG) parameters and to evaluate possible factors promoting SAECG parameters disturbances in the group of hemodialysis patients (HD-pts). 55 selected HD-pts entered the study. SAECG parameters (QRS duration, root-mean-square of the terminal 40 ms of the QRS--RMS40, low-amplitude signal duration--LAS40), were measured pre and postdialysis. Total (TBW), extracellular (ECW) and intracellular body water (ICW) calculated per kg of HD-pts body weight were estimated pre and postdialysis by using whole body bioimpedance. Two dimentional echocardiography was performed before HD. Serum levels of interleukin-6 (IL-6), tumor necrosis factor-alpha, CRP and intact parathormon were measured before HD. LP were found only before HD in 12.73% of patients. HD induced the decrease of LAS40 duration and the increase of RMS40 value in the of group of LP positive HD-pts (p<0.001 in both cases). The values of TBW and ECW calculated per kg of body weight as well as IL-6 and CRP levels were significantly higher in the LP positive in comparison with the LP negative patients (p=0.006 and 0.004 respectively). Induced by HD changes of RMS40 correlated with pre vs postdialysis values of TBW (r=0.499, p=0.001) and ECW (r=0.556, p<0.001) calculated per kg of body weight. Our study revealed that, that abnormal SAECG parameters and LP are frequently detected in HD-pts. The presence of LP in HD-pts in great part depends on the functional abnormalities (especially on the HD-pts hydration status) corrected by the HD process. The clinical significance of the proinflammatory factors (IL-6 and CRP) needs further investigation.