The synthesis of molecular carbon structures in the form of C60 and other fullerenes [1] has stimulated intense interest in the structure accessible to graphitic carbon sheets. High resolution transmission electron microscopy (HRTEM) was used to examine the morphology and structure of a new kind of fullerene, consisting of hollow graphitic carbon microtubules, discovered by Sumio Iijima in 1991 [2]. Electron microscope studies revealed that each needle-like tube comprises coaxial tubes of graphitic sheets, ranging in number from 2 to 50, separated by a distance of about 0.34 nm. Theoretical studies had been done before the large quantity (gram quantity) synthesis of the microtubules was developed by Ebbesen and Ajiyan [3]. However, further studies on these microtubules or even nanotubules are still limited to date. Here we present our X-ray diffraction (XRD) experiment results of mixed carbon microtubules. Microtubules were prepared by operating an arc discharge apparatus similar to that described in [3], with an a.c. potential of ~20V, in a helium atmosphere around 66.65 kPa (500 torr). The inner black core of the rod-shaped deposit was examined by HRTEM, as shown in Fig. 1. It can be seen easily that only a few nano-particles are contained in the hollow needle-like nanotubes. The samples used in the XRD experiments were prepared by grinding the inner core, as well as the original graphite electrode, to less than 300 mesh. Figs 2 and 3 show the powder diffraction results (20 from 20 to 100 °) of the samples (CuK~ radiation). Fig. 2 is in good correspondence with the well known results of graphite, which indicates that it is a hexagonal close-packed lattice. Thus it can be indexed easily according to JCPDS card no. 23-64, shown in Fig. 2. Table I shows the experimental results and calculated values of our test samples. Fig. 3 differs from Fig. 2, either in the intensities or in the peak positions, which clearly shows a crystalline structure, too. Fig. 3 shows the indexed result and the reasons are described below.