The large band gap semiconducting compounds of the type A^IIB₂^IIIC₄^VI crystallizing in the defect chalcopyrite (DCP) tetragonal structure are of great technological interest and have potential applications in non linear optical and photovoltaic devices. These compounds contain a crystallographically ordered array of vacancies (stoichiometric voids) in the cation sublattice and exhibit several interesting physical and chemical properties. The presence of the vacancies facilitates the doping of these compounds by impurities and has stimulated investigations about occurrence of order–disorder effects in the cation sublattice. In this presentation our recent experimental results on the high pressure investigations on some of the defect chalcopyrite compounds would be discussed.