Quantification of small solute removal in patients treated with chronic hemodialysis (HD) is widely used to assess the adequacy of both prescribed and delivered treatment. Four recent American studies have demonstrated a clear relationship between delivered dialysis dose and outcome in chronic HD patients. Although a number of HD quantification methods have been proposed, no specific technique is accepted as the gold standard at present. The primary goal of this review is to provide a critical assessment of the four recently published studies relating HD outcome to dialysis dose. As these studies involved a variety of therapy quantification methods, a review of the most common techniques used to measure dialysis dose is also presented. In addition, two unresolved issues that have recently come to the forefront of HD quantification are presented. These issues are the role of dialysate-side measurement of HD dose and the potential limit of the beneficial effect of increasing HD dose on clinical outcome. Finally, the overall design of the NIH HD adequacy trial is discussed, with particular attention paid to the kinetic methods used in the study.