Based on the work by Liu and Carter (1999, 2000), a framework for the compression behaviour of structured clays is proposed, in which two entities of an existing soil are differentiated and described clearly: the original structure of the soil and the destructuring the soil has experienced. A theoretical Compression Destructuring Line (CDL) is proposed to describe the whole destructuring process of soil from its original or un-destructured state. Soils of the same original structure form a unique CDL, irrespective of loading history or structuring/destructuring history. The "theoretical" original structure of a soil is represented by parameters A and c, which are detectable from compression tests on soil specimens with or without destructuring. The destructuring a soil has experienced is dependent on its current yielding stress and is quantified when the value of the yield stress is determined. The compression behaviour of four types of clay with twenty-two tests is then analysed. It is seen that the compression behaviour of clays with various structures is described well, and the magnitude of desctructuring can be quantified by the proposed method.