The components found in foxed areas and the formation of foxing by these components are reported. The authors have been studying foxing in order to clarify the formation mechanisms of foxing. Analysis of extracts of foxed areas showed that L-malic acid, cello-oligosaccharides, alpha-aminobutyric acid, aminoethanol, aspartic acid, glutamic acid, and ornithine were the characteristic features of foxed areas. Moreover, the authors experimented to see by what kinds of components, in what combinations and in what kinds of environments browning reactions appear. As a result, glucose and amino acids, especially gamma-aminobutyric acid, beta-alanine, aminoethanol, glycine, ornithine and serine, were found to react on paper causing browning, and foxing was formed. These results may suggest that foxing is caused by the Maillard reaction. -- AATA