Bioavailability and pharmacokinetic profiling of drugs and drugs in  formulations are very important to understand the rate and extent of absorption of drugs from the absorption site into systemic blood circulation, extent of distribution from blood to different sites of body and rates of their metabolism and excretion(elimination). Blood drug concentrations versus time data and profile may be correlated with the onset of drugs treatment effect, duration of effect, intensity of effect, duration of no effect and also the duration of side or unwanted effects. Blood drug concentrations versus time profile correlated with pharmacodynamic/clinical responses results in understanding  of therapeutic window of each drug that is constant for the treatment of specific disease. Treatment of any disease need multiple dosing. The desired target of any treatment is to maintain the fluctuating blood drug concentrations in therapeutic range only once the steady state is achieved after around 4to5 times of half-life of the drug. Pharmacokinetic studies help in designing the dosage regimen of a drug in a given formulation in order to specifically define the dose of a drug, its dosing frequency and also in some cases duration of treatment so as to achieve the safe and effective treatment of a disease. Through this talk, it will be discussed how to measure different bioavailability and pharmacokinetic parameters and what are their significances in achieving safe and effective therapy while treating a particular disease using a specific drug/formulation.