Line edge roughness is an important factor contributing to the problem of performance degradation in various nanoscale devices. We have developed two smoothing techniques based on nanoimprint lithography for the fabrication of nanoscale gratings with significantly reduced line edge roughness. Compared with other smoothing techniques reported before, our methods are low-cost, effective, and easy to implement. These technologies have been used for the fabrication of smooth nanochannels for stretching and separating double-stranded DNA molecules. They are also compatible with a wide range of materials and applications, including subwavelength optics, bioanalysis and micro/nano-fluidic systems. (C) 2003 American Vacuum Society.