yThe simulation of scanning tunneling microscopy images is performed ab initio with two readily available programs (Gaussian94 and a commercial spreadsheet). The model requires only a series of matrix multiplications and lends itself to widespread use. The versatility, reliability, and wealth of data one can obtain from the approach are illustrated by three examples: (i) benzene adsorbed onto the Rh(lll) surface, (ii) naphthalene on the Pt(lll) surface, and (iii) trans-2-butene on the Si(100) surface.