Lipid-based formulations, such as Self-Emulsifying Drug Delivery Systems (SEDDS), are an important tool for lipophilic drugs and offer the potential for enhancing drug absorption and oral bioavailability. SEDDS are a promising approach for the formulation of drug compounds with poor aqueous solubility. These systems are easily manufactured and physically stable mixtures of oil, surfactants, co-surfactants and solubilized drug substances that are administered orally in soft or hard gelatin capsules. In the gastrointestinal tract environment, these systems spontaneously emulsify. This review focuses on SEDDS formulations, describes their different types and presents case studies in which enhanced bioavailability were demonstrated in vivo using this formulation system.