['To compare and evaluate concentrations of hyaluronic acid (HA) in normal vocal folds of both young and elderly people of both sexes.', 'Experimental study.', 'The research was carried out at the ENT, Head and Neck Surgery Department and the Pharmacology Institute of São Paulo Federal University.', 'Enzyme-linked immunosorbent assay plates coated with biotin-conjugated binding protein and streptavidin-europium conjugate were sequentially incubated with samples from the middle portion of the cover, vocal ligament, and vocal muscle of 19 young and 20 elderly subjects of both sexes. After the release of europium in an enhancement solution, final fluorescence was measured using a fluorometer.', 'Statistically significant comparisons: (1) all subject groups combined exhibited a higher HA concentration in the cover and ligament compared with the muscle samples; (2) women subjects had a significantly lower HA concentration in muscle compared with the ligament, and male subjects showed significantly lower HA in muscle compared with the cover; and (3) both genders of young subjects showed a higher HA concentration in ligament samples compared with the muscle.'] Does concentration of hyaluronic acid in human vocal fold in young and old subjects?