The development of a highly controllable drug delivery system (DDS) for capsule endoscopy has become an important field of research due to its promising applications in therapeutic treatment of diseases in the gastrointestinal (GI) tract and drug absorption studies. Several factors need to be considered to establish the minimum requirements for a functional DDS. Environmental factors of the GI tract and also pharmaceutical factors can help determine the requirements to be met by a DDS in an endoscopic capsule. In order to minimize the influence of such factors on the performance of an effective DDS, at least two mechanisms should be incorporated into a capsule endoscope: an anchoring mechanism to control the capsule position and a drug release mechanism to control variables such as the drug release rate, number of doses and amount of drug released. The implementation of such remotely actuated mechanisms is challenging due to several constraints, including the limited space available in a swallowable capsule endoscope and the delicate and complex environment within the GI tract. This paper presents a comprehensive overview of existing DDS. A comparison of such DDS for capsule endoscopy based on the minimum DDS requirements is presented and future work is also discussed. © 2013 Elsevier B.V.