A lithospheric thermal model along a profile between the Pyrenees and the Balearic Promontory, coinciding with the Global Geoscience Transecs Project, is proposed. The numerical model is constrained by measured thermal data, crustal structure from seismic and grayimetric data, and uses thermal conductivity and heat production values from the literature. The best fitting model implies a lithosphere of 100 km below the Pyrenees in accordance with S-wave analyses. In contrast, in the Valencia Trough a thinned lithosphere of about 50 km is obtained. The temperature at the Moho is about 800°C between the Pyrenees and the Mediterranean coast, 400°C in the Valencia Trough and 600°C below the Island of Mallorca. Due to the absence of thermal data in Mallorca, three possible thicknesses (70, 80 and 90 km) have been tested, all yielding a similar surface heat flow of about 75 mW/m2. Lateral heat conduction is noted as being significant from the models. The ratio between the asthenospheric and surface heat flow (Qa/Qs) ranges between 0.45 in the Pyrenees and 0.9 in the Valencia Trough. © 1990.