Abstract Radiation, soil temperature at several depths and soil heat flux were measured in the U.K. and Syria. Diurnal variations are illustrated for areas of vegetation ranging from dense coniferous forest to bare soil. The soil heat flux is shown to be an important component of the surface energy balance, especially where ground cover is sparse, as in semi-arid regions. The direct measurement of soil heat flux has practical difficulties and its estimation from net radiation depends on the vegetation. The possibility of obtaining soil heat flux from simple soil temperature measurements independent of surface cover is discussed. The relationship between the daily rise in soil temperature and the energy absorbed at the soil surface is illustrated.