Relaxation processes are studied in silicon at high pressures. In the pressure range of 20-50 GPa, two firstorder phase transitions are observed in silicon. According to various estimates, the pressures at which metastable states exist are up to 10 GPa relative to the transition pressure. The boundaries of the metastable regions are determined. Relaxation times of the conductivity in silicon near pressure-initiated phase transitions are analyzed. It has been revealed that the relaxation time of the electrical resistance increases significantly when approaching the phase transition point. A pressure cell with diamond «rounded cone-plane» anvils are used to generate pressures.