Abstract 228 temperature measurements of 48 wells located in the northern part of the Nile Delta were used for obtaining geothermal gradient values at each well. Considering thermal conductivity values for the rocks forming the stratigraphic section in the Nile Delta to range between 2–2.3 w/m°C heat flow values over this part of the country were found to range between 39 and 56 mw/m 2. These values show the extension of the regional low heat flow that covers the Eastern Mediterranean area south to the northern parts of Egypt. Geothermal gradient values obtained at the 48 wells were used for compling maps of gradient variation over the study area. They were also used for calculating the depth at which 90°C and 150°C are expected. This range of temperature represents the probable liquid Hydrocarbon window, and depth and isopach maps for it are constructed. They show thicker window at Mit Ghamer, Tanta, Abu Qir, NAF, Tell El Ahmer, Wastani, and Qantara. These areas represent more potential areas if source rock is present. These results probably present additional informations for better assessment of oil and gas potentials of the Nile Delta.