INTRODUCTION The recent discovery of the existence of carbon nanotubes in the soot produced from the arc discharge of carbon electrodes, as well as the production of nanotubes in mac roscopic 23 has stimulated intensive research con quantities, cerning the structural and electronic properties of these inter- esting structures. Potential applications of carbon nanotubes include nanometer-size electronic and optical devices, and fiber reinforced material 4-3 There has recently been much theoretical work concerni ng the electronic structure of car bon nanotubes. It has been predicted that carbon nanotubes are metallic or semiconducting depending on the diameter d chirality of the nanotubes. Recently, scanning tunnel- and atomic force microscopy ing microscopy(STM) CAFM)s have been used to image carbon nanotubes. In this paper, we present STM images and STM current versus volt curves of carbon nanotubes hich show that aandatubes with diameters from 2.0 to 5.1 nma have a metallic debsity of states.