The lithosphere-asthenosphere boundary in the Valencia trough has been investigated by integrated geoid and gravity forward modelling along five regional profiles across the Trough. Our results show that the base of the lithosphere maintains an almost constant depth of about 60 km along the axis of the basin whereas the crust thickens in a NE-SW direction from 12--13 km to 19 km. These results suggest that a non homogeneous lithospheric stretching mechanism with a greater extension of the lithospheric mantle was responsible for the opening of the Trough, particularly in the southern area. ¿ American Geophysical Union 1996