ABSTRACTIndependent effects of fibre length and strength on the properties of pulp, and on the physical properties of the dry sheets have been demonstrated. Apart from improving formation, which indirectly influences many sheet properties, reducing fibre length has little direct effect on the sheet structural and optical properties, but does reduce mechanical properties. The loss in fibre strength also has little direct effect on the sheet structural and optical properties, but severely reduces those mechanical properties which are controlled by the breaking of fibres. Implications for market pulps are discussed.