Different methods for estimating land surface temperature for NOAA satellites data are presented. All these methods use the infrared channels of the Advanced Very High Resolution Radiometer (AVHRR). The single channel method using radiosounding data and a radiative transfer model is compared to the split window method and to other methods using additional High Resolution Infrared Radiation Sounder (HIRS) data. The results show the superiority of the split window method when the spectral variation of the surface emissivity between the two channels 4 and 5 of the AVHRR is negligible.