Two-step and three-step anneals were applied systematically to a set of commercial Czochralski silicon wafers. The microdefects generated during the anneals were decorated with Wright etchant and investigated by optical microscopy. The types of microdefect generated were observed to vary with the time and temperatures of the nucleation anneal. The observations provide very useful information relevant to the control of microdefects in Czochralski silicon to improve the gettering efficiency.