(1) Introductory remarks for the Fischer-Tropsch reaction in connection with various mechanisms so far proposed are presented briefly. (2) Our proposed mechanism is presented and discussed in detail. (3) The role of CH2 in hydrocarbon chemistry in general is stressed especially in connection with the Fischer-Tropsch reaction mechanism. (4) Approximate values of the activation energies for the reactions involved in the synthesis are presented and discussed in correlation with adsorption. (5) The aspect of polymerization process is discussed, and the question of surface migration is correlated with the polymerization reaction. (6) Adsorption and catalytic activity involved in the synthesis are discussed in the light of our desorption experiment. (7) The proposed mechanism is also applied to Fe type catalyst and discussed. (8) Various pretreatment effects on the catalytic activity are discussed in the light of our experimental evidences.