A review is given of reactions between structural defects and impurities in silicon which can effectively be utilized for the method of defect control in device production technology on the basis of the work of author's group. A theoretical treatment of impurity distribution around a structural defect in thermal equilibrium and experimental observations on dislocation pinning and thermal stability of precipitates formed on various types of structural defects give the general mechanism of impurity gettering at structural defects. Dependencies of the gettering efficiency at structural defects on the species and concentration of impurities, the cooling rate of crystal, and the type of structural defects are demonstrated with Fe and Cu impurities in silicon. The morphology of precipitates of supersaturated impurities formed on dislocations is shown to play an important role in strengthening of silicon wafers.