Efficient cross-linking of hyaluronic acid (HA) is provided by a manufacturing process. In the process, HA is activated by an initial cross-linking in an aqueous solution. Unreacted cross-linking agent is removed from the activated HA. Cross-linking of the activated HA is finalized, without addition of any additional cross-linking agent, in a suspension of a liquid precipitating medium and the activated HA in precipitated form. The resulting cross-linked HA products exhibit high effective cross-linker ratio and other favorable properties, making the products useful as implants and in medical and cosmetic surgery.