This paper reviews mechanochemical (MC) syntheses of functional materials by means of dry grinding operation without heating. First of all, the authors have shown that the MC reaction is dependent on not only material function such as Gibbs free energy change of formation (Delta G < 0) and structure type of the starting samples but also machine function enabling us to storage and accumulate the stress energy to the target materials. Then, they have concentrated the former one that the solid-phase reaction can be achieved by the necessary condition like Delta G < 0 as well as the structure of the starting samples. The first example is MC synthesis of perovskite complex oxides, ABO(3), where A and B trivalent oxides, respectively. Then, another type of complex ones such as ABO(4) from A(2)B(3) and B2O5, where B is pentavalent oxides, were shown. In these reactions, the structure of the starting samples are very important to determine the reaction completion or not. A reaction/non-reaction map has been introduced in this paper, and it is seen from the data that the radius (r(A), r(B) and r(O)) of the each metal elements in the reaction systems are crucial parameters in the reaction systems. The paper has extended to the synthesis of halides and sulfides conversion, and final example is a doping with non-ferrous metal element into oxide like TiO2, attempting the improvement of its visible light photoreactivity. These information would be helpful to understand and estimate the MC solid-state reaction of the starting materials. (C) 2012 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.