A method to measure “on site” programmed charges in EEPROM devices is presented. Electrical Scanning Probe Microscopy (SPM) based techniques such as Electric Force Microscopy (EFM) and Scanning Kelvin Probe Microscopy (SKPM) are used to directly probe floating gate potentials. Both preparation and probing methods are discussed. Sample preparation to access floating gate/oxide interfaces at a few nanometers distance without discharging the gate proves to be the key problem, more than the probing technique itself. Applications are demonstrated on 128 kbit EEPROMs from ST Microelectronics and 64 kbit EEPROMs from Atmel.