Changes in the physicochemical and flavor characteristics of the Okinawan brown sugar "Kokuto" during storage for 21 months at ambient temperature were investigated. Changes in moisture content and water activity were small. Decrease in L* value and increase in the color value were observed, and differences in color characteristics among different kinds of Kokuto reduced with preservation. The color value of Kokuto increased concomitantly with a decrease in free amino acid content. The change in polyphenolic content was small. The antioxidant activity of Kokuto increased till the sixth month and then decreased afterwards. During storage, the content of sulfur-containing compounds showed a large decrease, while the contents of 3-ethyl-2, 5-dimethylpyrazine and dihydro-2-methyl-3 (2H) -furanone increased. These results suggest that the Maillard reaction progressed during storage of Kokuto at ambient temperature. The degree of scattering of volatile compounds varied according to the samples of newly produced Kokuto; however, the difference in scattering reduced with preservation.