The effect of increasing the dialysate Na concentration on myocardial ischemia, assessed by ECG taken immediately before and after dialysis in 43 hemodialysis patients, was evaluated. An increase in the R wave (V5 + V6) by > 5 mm was seen in 26 patients with standard Na dialysate, while only 12 cases showed the same changes after a high Na dialysis. There was a positive correlation between an increase in R wave amplitude and the weight loss/dry weight ratio of patients only after standard Na dialysis (r = 0.74, P < 0.001). Relative high Na dialysate is beneficial during dialysis and reduces the incidence of myocardial ischemia and unpleasant disequilibrium syndrome.