A two-dimensional model of the fluid dynamics, heat transfer, molecular orientation and crystallization of the melt spinning of semi-crystalline compound fibers is presented. The model employs a Newtonian rheology, includes the effects of both temperature and flow-induced crystallization, and accounts for the effects of the molecular orientation on both the stress tensor and the crystallization through a Doi -Edwards formulation and the Avrami-Kolmogorov kinetics, respectively. It is shown that, even at moderately low Biot numbers, the temperature across the compound fiber is not uniform owing to heat losses; for the cases studied here, the temperature non-uniformities are mainly a function of the Biot number, the thermal conductivity and the pre-exponential factor and activation energy of the viscosity law for the cladding. It is also shown that the cross-sectional averaged temperature predicted by the two-dimensional model exhibits the same qualitative trends as those of an asymptotic one-dimensional model which does not account for axial conduction and which is only valid for slender fibers at low Reynolds and Biot numbers. (C) 2011 Elsevier Ltd. All rights reserved.