Drug delivery is process or method of administering a drug substance to achieve a therapeutic effect in humans or animals. Since it is expensive and complicated to discover and market new drug entity, so recognition of therapeutic advantages of new drug delivery systems with control over drug release has become important, and needs greater attention to develop such delivery systems. In last few decades extensive work has been carried out in order to have spatial and temporal control over drug release from delivery systems in the body; enhance and maintain quality of drug delivery systems during manufacture and storage; protect drug from physiological degradation; improve patient compliance and therapeutic outcome. While designing such release systems, it is important to identify and understand mechanisms involved in the release process. Mathematical analysis of the dissolution data/ release rates is used to accurately predict the drug release from the drug products which can ultimately help to optimize the design of a new drug delivery systems with desired therapeutic efficacy and safety. Here, a brief review of different techniques used for obtaining controlled drug delivery will be taken up for discussion along with mathematical models employed to study the release from such delivery systems.