An examination was made of the role of rainfall and runoff in soil loss from a krasnozem. Treatments included those of rainfall alone, runoff alone and rainfall and runoff together. Major soil losses were obtained when rainfall and runoff was applied simultaneously, minor losses occurred from rainfall and runoff alone. Using rainfall and runoff together, the effect of cultivation on the soil properties determining the erodibility of a krasnozem was studied. It was found that cultivation increases the erodibility of this soil and has more effect on the soil properties that affect infiltration rate than detachability. Aggregate stability studies demonstrated that changes in infiltration rate were correlated with changes in the stability of the soil aggregates to immersion wetting. Aggregates in the soils surface 1cm layer when wetted by high intensity rainfall behaved in a manner similar to when immersion wetted. It is concluded that infiltration rate is determined by the water stability of soil in the surface 1cm layer. Breakdown of the aggregates was due to air entrapment rather than raindrop impact. Soil conservation measures should be aimed at maintaining a high infiltration rate while preventing rainfall from making direct contact with any runoff water.