The microstructure (crystallinity, long spacing) and the micromechanical properties (microhardness H) of two series of nylon 6 and nylon 66 monofilaments and their blends were investigated as a function of annealing temperature T-A and uniaxial deformation in a wide composition range. In case of the homopolymers, the gradual rise of microhardness with T-A is interpreted in the light of the increasing values of the crystallinity alpha and the hardness of the crystals H-c. The depression of the hardness values of the blends from the additive behavior of the hardness of individual components is discussed in the basis of the crystallinity depression of one component by the second one and viceversa. Finally, the influence of drawing and pressing the blends at 130 degrees C which leads to a hardness increase is also explained in the light of an increase in the H-c value of nylon 66 due to orientation.