Degeneration of mixed Hodge structures Kazuya Kato Abstract. This is a joint work with Chikara Nakayama and Sampei Usui. In his great works on degeneration of mixed Hodge structures, Masaki Kashiwara formulated the notion "infinitesimal mixed Hogde module (IMHM)". IMHM appears when a variation of mixed Hodge structure degenerates. Nakayama, Usui and I obtained the theory of partial toroidal compactifications of the classifying spaces of mixed Hodge structures whose graded quotients are polarized. The points at infinity of these enlarged spaces are the classes of IMHM.