The vacancy defect subsystem is studied by means of electron microscopy in ion-implanted silicon. It has been discovered that, unlike the interstitial atoms which form rod-like defects and two-dimensional defects (dislocation loops, stacking faults), vacancies condense during annealing into three-dimensional associations—voids. The formation temperature of a void consisting of ∼103vacancies in 400–500°C. Voids have the tendency to associate into more complicated complexes; as a result of void interaction, disk-like clusters are formed in P+-implanted silicon. At temperatures 700–750°C, disk interaction is likely to take place which is accompanied by extended defect formation—chains. At annealing temperatures 800–850°C voids do not collapse in vacancy dislocation loops and chains do not rearrange in dislocations; all the defects dissolve in matrix.