An electron diffraction method is described and applied to analyze the atomic structure of individual tungsten disulfide (WS2) nanotubes. The method is based on a recently developed zoning scheme to determine the chiral indices of nanotubes by nano-beam electron diffraction. The chiral indices of a WS2 nanotube, which has its outermost shell missing on one end due to uneven growth of shells, is given to illustrate the indexing procedure. We also observed that the tubule chiralities within each WS2 nanotube display a mono-helical structure on average with a dispersion of a few degrees. (C) 2012 Elsevier B.V. All rights reserved.