Sustained release gastroretentive dosage forms enable prolonged and continuous input of the drug to the upper parts of gastrointestinal tract and improve the bioavailability of medication that is characterized by narrow absorption window. Gastroretentive floating drug delivery systems (GFDDS) of metformin hydrochloride, an antidiabetic drug with an oral bioavailability of only 50%(because of its poor absorption from lower gastrointestinal tract) have been designed and evaluated. Hydroxy propyl methyl cellulose(HPMC K4M) and carbopol 934P were used as polymers and sodium bicarbonate as gas generating agent to reduce floating lag time.Tablets were prepared by wet granulation method. Floating tablets were evaluated for hardness, friability, weight variation, drug content, floating properties and in vitro release pattern. The in vitro drug release followed first order kinetics and drug release was found to be diffusion controlled.