Hyaluronic acid (HA) is a long-chain biopolymer that is used for a wide variety of therapeutic purposes because of its high biocompatibility and advantageous physico-chemical properties. Typical uses include surgical preparations, adhesion prevention, viscosupplementation and drug and cytokine delivery. Storage and release of desired factors can be effectively achieved when HA-based carriers are synthesized as hydrogels, although doing so normally requires chemical modification of the native HA structure. Delivery of stored solutes from these gels can be either “simple”, that is from a gel not including separate components intended to control release, or “regulated” when specific components are included for that purpose. A diverse assortment of modified forms of HA has been developed and used in therapeutic, clinical, veterinary and laboratory research environments, and the number of such applications is likely to grow in future years. In this article, we review recent developments in this field.