This paper presents the results of a study conducted in the Mogi-Guaçu River basin (SP, Brazil) totaling an area nearly 11,600.00 km2 excluded urban areas, rivers and lakes. The main purpose was to generate information to support a program for erosion prevention and control for conservation planning in the area. The soil loss rates were estimated by USLE model and the lifetime index methodology was applied as a criterion to evaluate the soil loss tolerance and to interpret the soil erosion impacts on agricultural land. Originally, the lifetime index methodology identifies three different planning situations: 1) Conservation with adequate use, defined by the areas where the inferred soil renewal rate (0.2 mm.year-1) is larger than the current soil loss rates; 2) Lifetime zero in the present time, defined by the areas where the current solum (A+B) depth is smaller than a fixed value considered as the critical acceptable minimum depth; and 3) Control zone, defined by the areas where the estimated soil loss rates are greater than the inferred soil renewal rate (degradation situation) and the current solum depth exceeds the critical minimum pre-defined depth. In the control zone, the lifetime index allows to predict the time period (in years) when the pre-defined critical condition (extreme impact) will be reached. In the Mogi-Guaçu River basin, the lifetime index methodology was applied in a slightly different way. In this case, the aim was to estimate the time (in years) to lose the first 25 cm of the superficial soil (A horizon), usually the plus rich portion of the soil profile in organic matter and nutrients. The specific objectives were to evaluate the sustainability of the present agricultural land use and to identify the categories of land use that are greatly impacting land quality in the basin. The study was conducted with the software IDRISI 32 (Eastman, 1999), a raster Geographical Information System (GIS). The land use map was made using images from LANDSAT 5 TM. The images were pre-processed and georeferenced using the software ER- MAPPER v. 5.5. The generated 453 RGB false color composite was submitted to supervised classification and visual interpretation, using field reference patterns. The obtained results demonstrate that the planning situation Conservation with adequate use occurs in approximately 15% of the river basin area (1,796.69 km2), where the estimated soil loss rates are lower than the inferred soil renewal rate or lower than 0.2 mm.year-1. The categories natural vegetation (forest, savannas, riparian areas) and forestry (Pines and Eucalyptus) represent 38% of the use in the conservation area. The other land use categories occurring in this planning situation are annual crop/ pasture (32%), sugarcane crop (26%) and citrus and coffee plantation (4%). In the major part of the Mogi-Guaçu River basin, totaling 9,803.38 km2 or 85% of the evaluated area, the soil loss rates are greater than the inferred soil renewal rate and the soils are being degraded by accelerated erosion (control zone). The average soil loss rate is high, of about 51.26 Mg.ha-1.year-1, or 20 times greater than the inferred soil renewal rate. The lifetime index methodology was applied in the control zone and the results illustrate that keeping the present condition of land use and management, the first 25cm of the plus rich surface soil will be lost within 25 years in 50% of the evaluated area (4,901.69km2). In fact, the results support that for 32.71% of the area (3,206.95 km2) the lifetime index is merely 10 years or, in other words, the soil loss is nearly 2.5cm.year-1. Assuming that in the best estimate it is necessary 30 years to renew one inch of the superficial soil, then it is characterized an unsustainable situation of land use and management in these areas. The main categories of land use in this severe degradation situation in Mogi-Guaçu River basin are annual crops/ pasture and coffee and citrus plantation associated with Ultisols, Inceptisols and Entisols, occurring in steeper slope areas. The lifetime index methodology was useful to interpret the erosion process, to evaluate the sustainability of the present agricultural land use and to identify the categories of land use that are greatly impacting land quality in the river basin.