Synopsis Recent studies have shown that hyaluronic acid is an important molecule in cosmetics, although there are different, sometimes controversial theories about its role. This work is an analytical contribution to the characterization and control of hyaluronic acid. The main techniques used are UV, GCP or SEC, IR and corneometry. Surveys conducted with the aid of these techniques have allowed a better knowledge of the molecular weight determination and of the uniform quality of commercial supplies. These procedures may be of application for quality control and promote further investigation on the biological tissular role played by hyaluronic acid in topical cosmetic products. The analytical results of a study of the evaluation of oil/water (o/w) emulsions containing hyaluronic acid of different origins are reported. The analytical data obtained from cutaneous hydration control apparatuses were compared statistically. The choice of hyaluronic acid, made through screening and evaluation by the abovementioned techniques, ensures the optimal formulation of the finished product and a quality standard of the active principle.