Gastroretentive systems can remain in the gastric region for several hours and hence significantly prolong the gastric residence time of drugs. Prolonged gastric retention improves bioavailability, reduces drug waste, and improves solubility for drugs that are less soluble in a high pH environment. The present work describes the formulation and evaluation of gastroretentive system of an antiretroviral agent, Stavudine, based on the concept of altered density. Emulsion gelation technique was used to prepare the floating microcarriers using sodium alginate as the polymer. Microcarriers containing oil was prepared by gently mixing and homogenizing oil and water phase containing sodium alginate which was then extruded into calcium chloride solution. The prepared microcarriers were evaluated for drug entrapment efficiency, particle size and shape, micrometric properties, buoyancy and in-vitro drug release studies. The results of FTIR spectroscopy showed stable character of Stavudine. The mean particle size of microcarriers was in the range of 0.59-1.25mm. Microcarriers were spherical and free flowing. The drug entrapment efficiency was found to be 44.6-69.1%. The microcarriers remained buoyant for more than about 12h. The drug release study showed that Stavudine from the microcarriers was prolonged more than 10hrs. The results demonstrate that the amount of the oil entrapped in each microcarrier is play role in particle size entrapment efficiency and in vitro drug release