This paper contains a review of the history, natural occurrence, human consumption, metabolism, manufacture, and the results of eight standardized animal safety studies using trehalose. Trehalose (alpha,alpha-trehalose) is a naturally occurring sugar containing two D-glucose units in an alpha,alpha-1,1 linkage. Trehalose functions in many organisms as an energy source or a protectant against the effects of freezing or dehydration. It also possesses physical and/or chemical properties that are different than other sugars, which may make trehalose an attractive ingredient in food, health and beauty and pharmaceutical products. Data are presented supporting safe human consumption of trehalose in doses up to 50 g, and the physiologic ability of humans to digest it. No consistent treatment-related, dose-dependent adverse effects were observed in any of the eight safety studies performed at doses up to 10% of the diets. On the basis of these toxicity studies, human studies in which doses of trehalose were administered to various populations, and consumption of trehalose in commercial products in Japan, it is concluded that trehalose is safe for use as an ingredient in consumer products when used in accordance with current Good Manufacturing Practices.