It is estimated that 40% of active substances are poorly soluble in water. The improvement of bio-availability of drugs with such properties presents one of the greatest challenges in drug formulations. In recent years, there has been increasing interest in the use of formulations containing lipid based excipients that comprise combinations of synthetic or semisynthetic lipids with surfactants, co-surfactants or co-solvents. The lipid excipients based drug delivery such as Self emulsifying drug delivery system is one of the potential approaches for poorly soluble drugs. Self emulsifying drug delivery system (SEDDS), are isotropic mixtures of oils, surfactants, co-surfactants, can be used for the design of formulations in order to improve the oral absorption of highly lipophilic drug compounds. The following article present details on the lipid excipients used in the formulations, their biopharmaceutical aspects, factors affecting their selection for formulation, their role as surfactant, oil or co-surfactant and the various drugs that have been formulated with such type of systems.