The National Kidney Foundation K/DOQI Guidelines state that, "Serum prealbumin is a valid and clinically useful measure of protein-energy nutritional status in maintenance dialysis (MD) patients." Prealbumin, also known as serum transthyretin (TTR), was not recommended as a nutritional parameter of the same usefulness as the serum albumin. This decision was made, in part, because published research at that time suggested that serum TTR was not a more sensitive index of nutritional status than serum albumin and there was much more clinical and research experience with serum albumin as a nutritional and inflammatory marker. Evidence, including more recently published research data, which is reviewed in this paper has led to the following conclusions by the current authors: 1) In MD patients either protein-energy malnutrition or inflammation can lead to a reduction in serum TTR concentrations. 2) Hence, in MD patients, serum TTR concentrations can be used as a measure of both nutritional and inflammatory status. 3) Serum TTR concentrations are typically increased in MD patients. 4) In maintenance hemodialysis (MHD) patients, serum TTR is a risk factor for mortality that is somewhat independent of serum albumin. 5) Current epidemiological evidence suggests that a serum TTR value of 25 or 30 mg/dl or greater is associated with increased survival and, hence, is desirable in MHD patients. 6) MHD patients with serum TTR levels less than 25-30 mg/dl should be evaluated for protein-energy malnutrition and inflammation.