The aim of the present investigation was to develop a microsponge delivery system of acyclovir to control its release when applied topically thereby reducing dosing frequency and enhancing patient compliance. The microsponge was produced by oil in oil emulsion solvent diffusion method. The effect of different formulation and process variables such as internal phase volume, polymer type, drug polymer ratio, stirring speed and stirring duration on microsponge production yield, loading efficiency, particle size, and in vitro drug release was evaluated. The results showed that the microsponge F2 prepared from Eudragit RS polymer had optimum physical properties regarding loading efficiency of 99.71±0.7 % and production yield which was 85%. Also, F2 showed 66% drug release through 8 hours. Accordingly, the oil in oil emulsion solvent diffusion method is an effective technique to formulate microsponge with maximum production yields and loading efficiency for acyclovir.