Hydrodynamic Balanced Systems (HBS) can remain in stomach for long periods and hence can release the drug over a prolonged period of time. The aim of the present study was to develop a hydrodynamically balanced system of acyclovir as single-unit floating capsules. Low-density polymers were used for formulation and development of these floating capsules. The capsules were prepared by physical blending of acyclovir and various polymers in different ratios. The formulation was optimized on the basis of in vitro buoyancy and in vitro release in 0.1 N HCl. HPMC K4M gave the best in vitro percentage release and was found as the optimized formulation. By fitting the data into zero-order, first-order, and Higuchi models, we concluded that the release followed zero-order kinetics, as the correlation coefficient (R value) was higher for zero-order release.