Аннотация:This article presents the basic internal factors which determine loess collapsibility: composition and structure, porosity, structural bonds, natural water content. How these factors influence collapsibility is reviewed. The nature and mechanism of collapsibility are studied on the basis of structural changes. Structural bond strength reduction, the degradation of non-water- resistant microaggregates and the annihilation of capillary forces in water saturated loesses have been noted to play an important role in collapse development.