An overview is given on the solid-state addition reaction under mechanical stressing. Enhanced charge transfer across the boundary of dissimilar chemical species was observed mainly in terms of local polarization and/or radical formation. Associated anomaly of electron distribution is regarded mainly as a consequence of broken symmetry at various levels, i.e. molecular orbitals, crystal fields or ligand fields. A new preparation method of some ferrous coordination compounds is demonstrated. Recent preliminary results on some organic addition reactions are then displayed. Mechanisms of organic adduct formation via a series of Diels-Alder reactions are speculated. Outlook towards a new possibility of mechanochemical reactions in the direction of organic synthesis are also given. (C) 2004 Kluwer Academic Publishers.