Background and Aims: A bicarbonate dialysate acidified with citrate (CD) has been reported to have local anticoagulant effect and improves biocompatibility. This study examines the effect of CD on dialysis efficiency, coagulation, acid-base status, electrolytes, and inflammation in patients in on-line hemodiafiltration (OL-HDF). Methods: 35 patients in OL-HDF were enrolled in a prospective, cross-over study for a 24-week period and two phases alternating CD and acetate dialysate fluid (AD). Parameters on study were predialysis levels of bicarbonate and ionic calcium, reactive C Protein (CRP), and beta-2 microglobulin (B2MG) and postdialysis levels of activated tromboplastine time, bicarbonate, and ionized calcium. Results: No significant differences in coagulation parameters, pH, and predialysis bicarbonate were found. The postdialysis bicarbonate and postdialysis calcium were lower with CD. Dialysis efficiency was greater with CD. Regarding inflammatory parameters, both CRP and B2MG were lower using CD. Conclusion: The use of CD is safe and effective in OL-HDF, and it improves dialysis efficacy, postdialysis alkalosis, and inflammation.