A new experimental technique for evaluating the position of the oxide weak spot responsible for the stress-induced leakage current (SILC) in flash memories is presented. The oxide field along the channel is modified by drain biasing, and the gate current is then monitored. The position of the leakage spot can be determined by the shift in the gate current-voltage (I-V) characteristics. Experimental results on flash memory arrays reveal a strong localization of SILC in correspondence of the drain junction, due to the cooperation effects of program/erase (P/E) operations. The technique can be used to optimize the P/E conditions for maximum device reliability.