Despite the paucity of biopharmaceutic and pharmacokinetic data for many old drugs, these areas of scientific research have demonstrated an immense value in clinical medicine, and can be expected to expand man's knowledge of drug action and the influence of physiological function of drug disposition. Illustrated in this report are four major areas where biopharmaceutics and pharmaco-kinetics have contributed significantly to the field of medicine. Foremost among these contributions are: 1. the assessment of bioavailability and bioequivalence of new drugs and generic marketed drugs, respectively; 2. the pharmacolinetic characterization of new drugs and new drug delivery systems; 3. adjustment of dosing regimen; 4. assessment of kinetic profile of drugs in diseases state and dose adjustment thereof. Patient-drug pharmacokinetic profile designed to avoid toxicity is illustrated.