The soil strength as characterized by modulus of rupture (breaking strength) of moulded air-dried briquets and tensile strength (crushing strength) of natural and artificial soil aggregates was investigated as function of exchangeable cations, organic carbon, clay and clay plus silt content in 100 surface soil samples collected from the Hill-Bhabar-Tarai-Alluvial plain transect located in Gola and Kosi rivers inter-basin. Soil strength data indicate that organic carbon, type and level of exchangeable cations, clay, clay plus silt content of soil and interactions of these factors play significant role in controlling soil strength. In general, soil strength increased with increasing exchangeable Na+, clay and clay plus silt contents and decreased with increasing exchangeable Ca+. The effects of exchangeable Mg++, K+ and organic carbon on soil strength, are however variable. According to multiple regression analysis, 50 to 96 per cent variations in modulus of rupture, 35 to 91 per cent in tensile strength of natural aggregates and 63 to 97 per cent in tensile strength of artificial aggregates could be accounted to the combined effect of OC; exchangeable Ca++, Mg++, K+ and Na+; clay and clay plus silt contents of the soil. Further, the effect of these properties on soil strength was better expressed in coarse textured Hill and Bhabar soils (76–97 per cent) as compared to medium to fine textured Tarai and Alluvial plain soils (35–65 per cent).