The present communication reports the effect of a softening treatment carried out with 18% NaOH on the fine structure and structure-property relations in coir fibres. The effect of successive removal of lignin and hemicelluloses on the fine structure has also been studied. Unlike other cellulosic fibres, alkali treatment failed to produce any increase in fibre elongation in coir. However, the spiral structure was found to be considerably modified by swelling. X-ray and infrared spectral measurements revealed that a part of the noncellulosic components does occupy the intracellular space and plays a significant role on fine structural changes produced during the alkali treatment.