Nowadays, data retention, especially on extrinsic cells, is one of the main issues in the reliability of nonvolatile memories. The extrinsic data loss can be monitored with a test structure: the cell array stress test (CAST). Unfortunately, the extrinsic cells of a CAST cannot be easily quantified. In this paper, we present a new experimental method, based on the transconcluctance measurement of an EEPROM CAST, to quantify the extrinsic cells. This method has been verified by a method, based on emission microscopy, presented in a previous paper. (C) 2008 Elsevier Ltd. All rights reserved.