Poly(ethylene-2,6-naphthalate) fibers were zone-drawn under a critical necking tension (sigma (c)) defined as the minimum tension needed to generate a necking at a given drawing temperature (T-d) In the zone drawing under sigma (c) the neck was observed from 110 to 160 degreesC. The superstructure in a neck zone induced at each T-d was studied. The sigma (c) value decreased exponentially with increasing T-d and dropped to a low level at a higher T-d. The draw ratio increased rapidly with T-d increasing above 90 degreesC, but the birefringence and degree of crystallinity decreased gradually. To study the molecular orientation in the neck zone, we measured a dichroic ratio (A(/) /A(perpendicular to)) of a C-O band at 1256 cm(-1) along a drawing direction in the neck zone with a Fourier transform infrared microscope. A(/)/A(perpendicular to) at T-d = 110 degreesC increased rapidly in the narrow neck zone, and that at T-d = 140 degreesC increased in the edge of the wide neck zone. Wide-angle X-ray diffraction patterns of the fibers obtained at T-d = 130 degreesC and lower showed three reflections due to an alpha form, but those at T-d = 140 and 150 degreesC had reflections due to the alpha form and a beta form.