The kinetics of electrical deactivation of As-doped silicon was studied at temperatures from 450 to 700 degrees C by using samples doped in the range from 1 x 10(20) to 1.7 x 10(21) cm(-3). Twelve types of specimens were obtained by As implantation at 100 keV of both silicon on insulator (SOT) and bulk Si wafers, followed by damage removal by furnace annealing, ruby, or alternatively excimer, laser pulses. Accurate determinations showed that the kinetics of As clustering complies with the zero order rate equation: -dn/dt = A exp[-(E-alpha n)/kT], which describes the deactivation process until the reaction is close to the equilibrium. The activation energy, E, is found to be 1.9 eV, for all compositions and preparation techniques. Both A and alpha are independent of temperature and depend on total As concentration, C-As. With increasing C-As, alpha decreases according to the empirical formula: alpha = 1.6 x 10(-21)[1 + 5.5 exp(-C-As/1.8 x 10(20))] eV cm(3) valid for C-As up to about 1 x 10(21) cm(-3). The effective activation energy, E - alpha n increases with decreasing the carrier density and, vice versa, it becomes vanishingly small at high As+ concentrations. Carrier concentrations higher than 4 x 10(21) cm(-3) are unstable even at room temperature. The pre-exponential factor, A,increases markedly with C-As according to the empirical relation: log A = 26.6-6.5 x 10(10)/(C-As)(0.5) cm(-3) s.(-1) The hypothesis is advanced that the increase of A is due to the increase of suitable atomic arrangements for clustering, with As in second neighbor (N-As)(NNN) lattice positions.