Raman microscopy is applied to a gel-spun UHMWPE-fibre (Dyneema SK60) to determine the distribution of axial molecular stresses and their change with time (in creep and during stress relaxation). A more detailed method is proposed to quantify the observed characteristic changes in local stress distribution. The increase in highly overstressed bonds (5 8 GPa) is ascribed to the straining of tie-molecules during creep. Their pull-out, crystal plasticity and grain-boundary slip determine stress relaxation. A refined structural model of the UHMWPE-fibre is proposed, which is used to discuss the still existing difference between theoretical and practical strength of such fibres.