We have previously concluded that the oxygen-precipitate-associated defects that we identified by the deep levels at Ev+0.30 eV and Ec-0.25 eV were the Pb centers generated in the interface between the oxygen precipitates and the surrounding silicon crystal lattice [M. Koizuka and H. Yamada-Kaneta, J. Appl. Phys. 84, 4255 (1998)]. In order to confirm this conclusion, we have made electron spin resonance (ESR) measurements on the Czochralski-grown silicon crystals containing the oxygen precipitates generated by the two-step anneals of 500 °C, 20 h+700 °C, 60 h. We have found the ESR lines whose g values well coincide with those of the Pb0 and Pb1 centers. Thus it has been clarified that the Pb0 and Pb1 centers are generated by the oxygen precipitation as well as by the thermal oxidation. The present successful application of the ESR method to the annealed silicon crystals suggests that it can be a useful tool to characterize the precipitation state of the oxygen in silicon. © 2000 American Institute of Physics.