Polymeric hydrogels have been applied as functional materials in many fields. In particular, stimuli-responsive hydrogels which change swelling-shrinking in response to external stimuli become noteworthy intelligent materials to control of drug delivery. In conventional “drug delivery system (DDS)”, hydrogels have enabled constant release rate for a long period or sigmoidal release by their characteristic swelling behavior. Swelling behavior of gels have been effectively utilized to control drug release rates. In recent years, in addition to rate control, temporal control of drug delivery has been of interest to achieve improved drug therapies. Intelligent DDS are one expected result, demonstrating an ability to sense external environmental changes, judge the degree of external signal, and release appropriate amounts of drug. Some polymeric hydrogels demonstrate markedly swelling-deswelling changes in response to enternal stimuli. Such phase transition of gels are attempted to apply to stimuli-responsive drug release systems, and achievement of intelligent DDS are expected with these hydrogels. In this review, recent studies on rate and temporal control of drug release using polymeric hydrogels are described. Swelling and deswelling dynamics of gels as controlling mechanism of drug release will be discussed, mainly focused on temperature-responsive poly(N-isopropylacrylamide) gels.