We have obtained high-resolution scanning tunneling microscopy (STM) images of Escherichia coli lysine transfer ribonucleic acid (tRNA) adsorbed onto Cu(111) substrates using a pulse injection method. One of the two arms of the L-shaped structure of the observed tRNA is longer than the other. Because hydrogen bonds that maintain the unique three-dimensional structure of tRNAs exist in the hinge region and in one arm of L-shaped structures that include the anticodon stem, we concluded that the longer arm in the L-shaped structure includes the anticodon stem, and the shorter arm includes the acceptor stem. This work supports the view that STM is a powerful tool for obtaining high-resolution images of biomolecules that are too difficult to crystallize. (C) 2003 American Vacuum Society.