Surface heat flow gives direct information about geothermal gradient, but it is significantly affected by erosion and sedimentation. The rate of erosion (sedimentation) is generally in proportion to elevation. Following such an idea, first, we examined the relation between observed surface heat flow and elevation along each of three lines crossing the northernmost, northeastern and southwestern parts of Japan, and found a clear positive correlation between them. The good correlation indicates essential importance of the effects of erosion and sedimentation on surface heat flow. Next, assuming the linear dependence of erosion rates on elevation, we calculated the profiles of surface heat flow expected from the surface topography with a 2-D thermal conduction model. The results of calculation well explain gross features of the observed heat flow profiles, but some systematic differences still remain. From these systematic differences we can extract unbiased information about thermal state at depth. ¿ 2001 American Geophysical Union