The purpose of writing this review article on gastro- retentive drug delivery systems (GRDDS) have been developed; the principle mechanism of floatation to achieve gastric retention. The recent developments of (FDSS) including the physiological and formulation variables affecting the gastric retention. Several techniques such as floating drug delivery system, low density systems, raft systems, mucoadhesive systems, high density systems, super- porous hydro- gels and magnetic systems, have been employed. Floating drug delivery systems have a bulk density less than gastric fluids and so, remain buoyant in the stomach for a prolonged period of time, releasing the drug slowly at the desired rate from the system. Dosage forms available as gastric floating systems include tablets, capsules, granules and microspheres.