The thermal regime of Algeria and Tunisia and its relation to hydrodynamics is studied by means of available geological and geothermal, and petroleum data. Heat flow densities in the area range from 60 mWm (super -2) to 141 mWm (super -2) . Several Paleozoic to Tertiary aquifers have been identified, together with potential recharge and discharge areas. The area is a transition zone between the African and European plates. The more tectonically active northern Alpine domain does not exhibit an obvious geothermal trend, and high heat flow anomalies that occur there may be related to structure rather than hydrodynamics. The more stable southern Saharan tectonic domain, with background heat flow of approximately 80 mWm (super -2) , exhibits anomalous zones correlated to the hydrodynamic regime with low values in recharge areas (Algerian Tinrhert and High Plateaux) and values in discharge areas (Tunisian Jeffara and Algerian Tademait). The hydrodynamic perturbation to the normal heat flow is estimated to be as great as 10 - 20 mWm (super -2) in recharge and discharge zones.