The study was carried out (i) to monitor the spatial extent of salt-affected soils and (ii) to assess the efTect of image scale on the delineation of these soils using Landsat data in the Indo-Gangetic plains of Uttar Pradesh, northern India. Monoscopic visual interpretation of standard false colour composile (FCC) prints of Landsat-MSS data acquired in 1975 and of Landsat-TM data acquired in 1986 was carried out to delineate salt-affcted soils during these two periods. Salt-affected soils could be categorized as saline sodic soils and key out as Typic Natrustalfs, A shrinkage in the areal extent of salt-affected soils to the extent of 9–9 per cent was observed during an 11-year period which could be attributed to ameliorative efforts by the farmers and to state and central Government agencies.