Oral delivery of complex molecules such as peptides and proteins is one of the most intensively studied research subjects. However, its success has been hampered by the degradation of these molecules in the gastrointestinal tract. As a result, various types of particulate systems such as biodegradable microspheres and liposomes have been proposed as potential delivery vehicles to protect these drugs in the gastrointestinal tract. Unfortunately, these particulates generally display low oral absorption efficiencies. This renders most encapsulated drugs ineffective after oral administration and therefore remains as the main obstacle to their practical application as oral delivery vehicles. In attempts to improve particle absorption efficiency, strategies such as using mucoadhesive polymers and targeted delivery systems have been studied in animals. In this chapter, the usefulness of these strategies are briefly reviewed. Potential applications and future prospects of particulates in oral delivery of complex molecules are also highlighted.