We have discussed the basic principles of pharmacokinetics and convective solute removal in the context of each other. Clinical observations appear to follow the theoretical expectations. For practical purposes plasma and plasma water are not different. In the calculation of drug sieving, venous samples do not contribute enough to warrant their extra costs. We recommend that drug removal in hemofiltration be expressed by the sieving coefficient, UF/A. Drug sieving data in humans undergoing CAVH are tabulated. Recommendations for supplemental dosing are discussed which are applicable to any clinical setting.