The elimination of substances during hemofiltration depends on the special properties of the used wide-porous membranes. High filtration-fractions are achieved and, in practice, all substances with a molecular weight below 10,000 Dalton pass the membrane. Also drugs are filtrated equivalent to their unbound free plasma-fraction. A quantitative elimination of drugs during hemofiltration is to expect, 1. if a sufficient ultrafiltration rate of 10 ml/min or more is reached, which is the upper limit of spontaneous CAVH, 2. if the sieving-coefficient or plasma-protein-binding enables a sufficient passage and 3. if the serum concentration of the drug related to its administered dose is high, i.e. the volume of distribution is small. An adjustment of drugs is partially necessary during hemofiltration. A simple way is to calculate the total creatinine-clearance to derive dosage modifications.