Homogeneous catalyses promoted by transition metal complexes such as cross coupling reaction, Mizoroki-Heck reaction, Tsuji-Trost allylation reaction, functionalization of C-H bond, Sharpless oxidation reaction, and some recent topics related to organotransition metal complexes are described. Mechanistic aspects of these reactions are also discussed based on the fundamental reaction patterns of organotransiton metal complexes. Future perspectives of organotransition metal catalyzed reactions are also described.