Drug dosing in renal insufficiency needs to be individualized whenever possible to optimize therapeutic outcomes and to minimize toxicity. Although a number of published tables that provide dosing guidelines and nomograms exist to assist in dose modification, individualization of therapy should be based on pharmacokinetic principles whenever possible. The basis equations to estimate the pharmacokinetic parameters of clearance, volume of distribution, and half-life for intravenous drug administration of drugs with first-order kinetics are not difficult to understand and apply. Their use should be encouraged in patient care.