Preliminary results are presented from the study of grain boundary structurein bulk nanocrystalline copper using high-resolution electron microscopy. A recently developed method of image analysis is applied to an experimentalimage of a grain boundary between two copper grains. Maps are produced ofthe fringe spacing and the local rotation of the lattice as a function ofposition in the image. The analysis of the fringe spacing shows that nooxide layer exists between the copper grains. This confirms that thesurface oxide layer coating the copper particles can be eliminated duringthe formation of the bulk material. By studying the way the rotation of thelattice takes place across the grain boundary, an upper limit for theinterface width is obtained. The reliability and accuracy of the resultsare discussed.