High-resolution electron microscopy (HREM) has been widely used in studies of fullerene-related carbons, and in particular has been applied extensively to the study of carbon nanotubes (Iijima, 1991; Ebbesen & Ajayan, 1992) and carbon nanoparticles (Harris et al., 1993; Saito et al., 1993). The purpose of this Note is to draw the attention of workers in this field to the fact that carbon nanotu...