Rheology and stress relaxation dynamics of a well-characterized, entangled polystyrene/ diethylphthalate solution are investigated during start-up and following cessation of steady shear flow. Rheological measurements designed to probe the effect of flow-induced changes in polymer relaxation time on properties form the main focus of this study. At shear rates gamma intermediate between the reciprocal terminal relaxation time 7-do and reciprocal longest Rouse relaxation time tau(Rouse)(-1), we find that both convective and nonconvective processes accelerate molecular relaxation in entangled polymer liquids. The former processes are described well by the multimode convective constraint release model of lanniruberto and Marrucci (2002), but the latter ones are not. At shear rates gamma < tau(Rouse)(-1), the nonconvective processes give rise to a two-stage relaxation mechanism following cessation of steady shear flow. The first stage of relaxation is characterized by a time constant tau(Recv) (1) that is over an order of magnitude greater than tau(Rouse) and is a decreasing function of shear rate tau(Recv) (1) similar to gamma(-0.4), while the second stage is characterized by a shear-independent characteristic time tau(Recv) 2 approximate to tau(d0). We also find that overshoots in first normal stress difference N-1 begin at shear rates substantially lower than tau(Roluse)(-1), and that the effect of shear rate on the size of NI overshoots is qualitatively different from theoretical predictions. Q 2003 The Society of Rheology.