The connection between hyaluronic acid and phagocyte function is not well documented in the literature. Its action may either inhibit or enhance polymorphonuclear neutrophil (PMN) function, depending on its concentration. Studies were conducted to verify the effect of hyaluronic acid on phagocytes, both directly using hyaluronic acid and indirectly via a mediated route using the medium from a hyaluronic acid monocyte incubation. Determinations were made of phagocytosis, reduction of nitroblue tetrazolium, superoxide production, and chemotaxis before and after incubation with hyaluronic acid. Chemotaxis of PMNs was used to evaluate the chemotactic action of a medium in which monocytes had been incubated with hyaluronic acid. This method resulted in progressive improvement in the chemotactic index. The authors conclude that the monocytes incubated with hyaluronic acid produce a chemotactic factor for neutrophils.