We evaluated the feasibility of using L-lactate as a base for hemodialysis. In one study, acid-base changes using 40 mM L- or DL-lactate were compared. In a second study, acid-base status using various amounts of L-lactate exclusively was studied. The third study compared symptoms and acid-base changes during 9 weeks of high-efficiency dialysis when using L-lactate, acetate, or bicarbonate as base. In the first study, plasma bicarbonate changes were equivalent with 40 mM L-lactate and 40 mM DL-lactate, but overall correction of acidosis appeared to be suboptimal. In the second study, when compared to a bicarbonate control period, correction of acidosis was reduced when using 40 mM L-lactate + 4 mM acetate solution, but increased when using a 46 mM L-lactate + 4 mM acetate solution. In the third study, correction of acidosis was comparable when using 42 mM L-lactate + 4 mM acetate, 39 mM acetate, or 35 mM HCO3 + 4 mM acetate. Whereas 46% +/- 12 (SEM) treatments "failed" because of symptoms when using acetate, the percentages of "failed" treatments were only 7% +/- 4.2 with L-lactate (p less than 0.05) and 11% +/- 4.2 with bicarbonate (p less than 0.05). The results suggest that L-lactate is a suitable dialysis solution base that is capable of correcting chronic uremic acidosis. During high-efficiency dialysis, the incidence of intradialytic symptoms with L-lactate is comparable to that with bicarbonate and less than that with acetate.