The kinetics of thiourea Synthesis of CdS nano particles (NPs) in reverse- microemulsions of Tergitol Np-4/n-decane was studied in the. temperature range of 313-333 X by spectrophotometry, photon-correlation spectroscopy, and transmission electron microscopy. The formation of NPs is described by the kinetic model, including two consecutive steps: homogeneous nucleation in a solution as the first step and the autocatalytic growth of NPs due to heterogeneous reaction on a continuously increasing surface as the second step. Effective rate constants of the steps (k(1) = 1.52 X 10(-2)-1.75 x 10(-3) s(-1) and k(2) = 4.9 x 10(-1)-5.1 X 10(-2) M-1 s(-1)) and effective activation energies (E-a1 = 156 and E-a2 = 149 kJ/mol) were estimated in the pseudo-first-order reaction with respect to cadmium (c(cd) = 0.9 mM, c(Thio) = 9 mM). The obtained constants were used to calculate the dependence of nanopartide diameter on the synthesis tune (d(3) similar to t). The calculated values correlate well with experimental data of photon-correlation spectroscopy and transmission.electron microscopy.