The rheological behaviour of a linear low density polyethylene melt is studied using a wide range of techniques: shear and elongational stress growth at constant strain rate, steady shear flow, extrudate swell and isothermal melt spinning. The analysis of the behaviour is based on the Wagner constitutive equation which appears to be suitable. Moreover, the extrudate swell and the isothermal spinning are simulated by taking into account. the past shear and elongation deformation in the reservoir, the contraction and the die of a capillary rheometer. For this purpose, the Finger deformation tensor is evaluated using a Protean coordinate system. This approach is shown to be very useful to rest the validity of the constitutive equation and to determine its characteristic parameters.