ABSTRACT:Circadian and other biological rhythms affect diseases, there symptoms and severity of symptoms and drug therapy can be modified keeping these variations under consideration. Chronopharmacology refers to the manner & extent to which the kinetics and dynamics of medication is directly affected by endogenous biological rhythm and also how the dosing time of medications affects biological timekeeping & features. It has a number of advantages as it reduces drug dosage, increases therapeutic efficacy of drug, limits the time of therapy, reduces side effects, slows down speed of progression of disease and especially helpful in preventing drug toxicity in case of compromised body systems. There is a great deal of interest in how chronotherapy can particularly benefit patients suffering from allergic rhinitis, rheumatoid arthritis and related disorders, asthma, cancer, cardiovascular diseases, ankylosing Spondylitis, renal disorders, antimicrobial therapy, diabetes mellitus, ant-inflammatory therapy, peptic ulcer disease etc. Various drug delivery systems have been developed like pulsatile drug delivery systems, Enteric-coated systems, Layered systems, time-controlled explosion systems (TES), sigmoidal release systems (SRS), electric based drug delivery systems system, controlled-release microchip, etc for effective chronotherapy. There is great deal of hope for effective drug therapy using chronopharmacology in near future.