A model is proposed for the description of the viscoelastic and yield behaviour of polymer fibres. It involves the introduction of activated transitions with relaxation times that are a function of the stress. This is analogous to the introduction of an Eyring reduced time. These transitions govern the shear deformation of a domain, being the building block of the continuous chain model for the tensile deformation of polymer fibres. The main features of the viscoelastic behaviour of fibres have been derived. They are the rate dependence of the yield stress, the transition from a concave creep curve for a stress below the yield stress to the logarithmic behaviour for stresses above the yield stress, the creep rate of a fibre, the disappearance of the yield for increasing temperatures and the response to complex loadings. (C) 2003 Published by Elsevier Ltd.