Relations among warpage, material anisotropy, and part thickness were numerically investigated for disks injection molded from PA66 compounded with 33 wt% glass fiber. Finite element analysis was used for calculating now fields in injection, fiber orientation, material anisotropy, and warpage. Volume averaged anisotropy has been introduced, which is a ratio of the volume averaged linear thermal expansion coefficient in the flow direction to tile coefficient in the direction transverse to flow ([R alpha] = [alpha(11)]/[alpha(22)]). Good agreement has been obtained between calculation and experiment with respect to [R alpha]. A mechanical quantity, (Delta T)(b)/h(2), which is the buckling temperature divided by the square of disk thickness, is also introduced. Differences in mechanical behavior between an injection molded disk and a composite laminate disk have been shown. A linear correlation between the mechanical quantity and the material anisotropy is also found. Parameters that determine the disk warpage are deduced from the correlation. The correlation for the injection molded disk is found to be a subset of the correlation for the composite laminate disk. The correlation between [R alpha] and (Delta T)(b)/h(2) has been extended so that the relation is applicable not only io anisotropic materials but also to isotropic materials.