The efficacy of intradialytic parenteral nutrition (IDPN) in malnourished hemodialysis patients was studied. All patients at a large tertiary care institution who received IDPN for one month or longer between June 1997 and December 2000 were included in the study. The IDPN formulation contained 10% amino acids 250 or 500 mL, 50% dextrose 250 mL, and 20% fat emulsion 250 mL. IDPN was administered during each thrice-weekly hemodialysis session. Patient data were collected 6 and 3 months before IDPN therapy began, at baseline, and 3, 6, 9, and 12 months after the therapy began. Therapeutic efficacy was assessed by the percent change from baseline in dry body weight and serum albumin concentration. Twenty-six courses of IDPN in 24 patients met the study's inclusion criteria. The mean duration of treatment was 4.3 months. Dry body weights were significantly lower 6 and 3 months before the start of IDPN therapy than at baseline and significantly higher 6, 9, and 12 months after the start of therapy. Serum albumin levels were also significantly higher at 3 and 9 months than at baseline. The percentage of treatment courses in which patients had a serum albumin concentration of > or = 34 g/L was 12% at baseline, 39% at 6 months, and 47% at 9 months. Adverse effects consisted primarily of excess fluid gain and hyperglycemia. IDPN therapy significantly increased body weight and serum albumin levels in malnourished hemodialysis patients.