As part of an international experiment in which several methods of estimating the actual evapotranspiration were compared, two large aperture scintillometers (LAS) and a small micrometeorological station were installed in the Gediz Basin near Menemen, Turkey during the summer of 1998 by the Meteorology and Air Quality Group of the Wageningen Agricultural University. The instruments will be used to provide "ground-truth" sensible heat fluxes. At the first site, a LAS was set up over a transect of the valley from Belen to Suluklu with a path length of 2700 m. The second LAS (a path length of 670 m) together with a small micrometeorological station was installed in an irrigated cotton field west of the first site. However, due to experimental problems the scintillation method for the second site could not be applied. Instead the variance method, which just as the scintilliation method is based on the Monin–Obukhov similarity theory, was used. The 24 h average sensible heat fluxes of the valley for the entire growing season are presented and special attention is given to the LANDSAT overpass dates June 26 and August 29. The results presented in this paper show that the scintillometer is a robust and reliable "stand-alone" system that is able to provide operational estimates of areal averaged sensible heat fluxes.