Within the skin tissues, acidic mucopolysaccharides such as hyaluronic acid are present in the corium layer and play a large part in water retention and skin resilience. Hyaluronic acid is a polymer composed of dimers containing N-acetylglucosamine and glucuronic acid. Although applications of the use of hyaluronic acid in cosmeceutical food have been reported, the beauty efficacy of orally-ingested hyaluronic acid cannot be predicted adequately because little is known about its digestion and absorption in humans. The purpose of this study was to investigate the effect of long-term oral N-acetylglucosamine supplementation on skin conditions in females who have a common tendency of xeroderma and rough skin. The subjects (average age: 25.5 ± 10.7) were assigned randomly and double-blind to either a N-acetylglucosamine group (n=11) or a placebo group (n=11), and ingested a daily 1000-mg dose of N-acetylglucosamine or lactose, respectively, for 60 days. Dermatological examination by doctors suggested that N-acetylglucosamine supplementation favorably affects skin conditions; that is, improvements were observed in the desiccation of facial and whole body skin. After N-acetylglucosamine supplementation for 60 days, the moisture content of the region below the left eye was increased significantly; conversely, a significant decrease in the oil and fat content was observed. In addition, clinical evaluation by a microscopic three-dimensional skin surface analyzer confirmed that oral N-acetylglucosamine supplementation is useful for mitigating the roughness of the skin and the epidermolysis of the corneum. These results indicate that oral N-acetylglucosamine supplementation may be of benefit in enhancing skin hydration. By contrast, no significant improvement was observed in the skin condition of the placebo group, as appraised by either dermatological examination or digital analysis. The beautification effect produced by ingestion of N-acetylglucosamine indicates that this compound may be a potential ingredient for cosmeceutical foodstuffs.