A variant was proposed in the technique of Venturini and others for the estimation of the density of instantaneous latent heat flux in regional scale based only on remote sensing, by introducing a new expression for the calculation of the relative evapotranspiration. A discussion of the physical meaning of the variables involved and the validity of expressions proposed for its calculation was carried out. Maps of ET in the province of Buenos Aires were estimated for the first time, in several days of summer. It was found that obtained spatial variations of ET present a proper relationship with the surface temperature and NDVI values obtained from MODIS products. It was proved as per statistics that, on having replaced the values of air and dew point temperatures at the surface by information in 1000hPa of the MODIS products, significant errors interfere. The obtained values of albedo, incoming shortwave radiation, incoming and outgoing long-wave radiation, and instantaneous flux of latent heat of vaporization, are within the range expected in accordance with measurements and estimates made by other authors in locations interior to the study region and in other regions.