Increasing use of medications designed specifically for intravenous administration during hemodialysis has dramatically improved the treatment of many comorbid conditions accompanying end-stage renal disease. Recombinant human erythropoietin has resulted in definitive treatment of the hypoproliferative anemia of uremia, while sustained response to this hormone has been facilitated by treatment with intravenous iron dextran. Simple and effective therapies for many gram-positive infections in end-stage renal disease patients have been realized through the favorable pharmacokinetics and low toxicity of vancomycin when administered during hemodialysis. Major improvements in the therapy of high-turnover bone disease have resulted from the increasing use of intravenous calcitriol during dialysis as well. The contributions of these four medications in improving patient care and the benefits of their administration during the dialysis procedure are reviewed.