The thermal behavior of polyamide 6/amorphous polyamide blends has been investigated as a function of blend composition and temperature. Crystal phase nature and stability are probed by a combination of thermal analysis, X-ray diffraction and Fourier transform infrared spectroscopy. Ductility appears to be strongly affected by the addition of the amorphous polyamide, but the corresponding decrease of the yield stress, either taken at the same draw temperature or under a comparable state of mobility of the amorphous phase, may not be simply accounted for by the reduction of overall ordered phase content.