A method for determining the original position of a wafer in an ingot made from semiconductor material comprises the following steps: measuring the interstitial oxygen concentration in an area of the wafer; measuring the concentration of thermal donors formed in said area of the wafer during a previous solidification of the ingot; determining the effective time of a thermal donor formation anneal undergone by the wafer when solidification of the ingot took place, from the thermal donor concentration and the interstitial oxygen concentration; and determining the original position of the wafer in the ingot from the effective time.