Kinetics of changes in sizes of phase regions and volumes at the early stages of the phase separation of glasses in the PbO-B₂O₃ system has been studied using smallangle X-ray scattering (SAXS). The existence of the interval of heating durations in which the changes in the sizes of the phase regions and volumes are small so that it is possible to approximately consider that the structure is in a relatively stable state has been experimentally established. The relative phase volumes and compositions in glasses of the studied system are close to the equilibrium ones already for the sizes (radii) of the regions of the separated phase of about 15- 20 Å and the Ostwald ripening (coalescence) stage begins. Maxima due to the interparticle interference have been observed in the angular dependences of the SAXS intensities. This indicates ordering in the distribution of the phase regions.