Pharmaceutical drug delivery embraces a range of delivery carriers and constructs that have dimensions ranging from several nanometers (nanotechnology) to numerous millimeters (conventional dosage forms, i.e., pellets, tablets, and capsules). Such delivery systems spawn a whole array of assemblies for delivery of highly potent active drugs through different routes of administrations to numerous sites and targets in the human or animal body to treat disease conditions. This chapter highlights the potential uses of hard shell capsules as carriers for extended-release drug delivery systems that, by virtue of their design and popularity, satisfy features of an ideal technology platform for drug delivery and reliable pharmaceutical production. Modified-release drug delivery technologies, which include both enteric-coated systems and a variety of controlled-release solid dosage forms, including capsules, have evolved as a multidisciplinary science. Modified-release capsules encompass both enteric and extended-release products.