Adhesion forces between well-ordered organomercaptan monolayer films strongly bound to both a Au substrate and a microscopic Au probe were measured over separations ranging from similar to 10 nm to repulsive contact and probe radii from 50 nm to 60 mu m using interfacial force microscopy. Films terminated with methyl groups (CH3 vs CH3) were examined and these results are contrasted with hydrogen-bonding (NH2 vs NH2 and COOH vs COOH) and acid-base (NH2 vs COOH) combinations. From the peak value of the adhesive pull-off force, we calculate interfacial bond energies using a model that has been shown to be applicable in such situations. These values qualitatively scale with those expected for van der Waals, hydrogen-bonding, and acid-base interactions. The force-versus-displacement behavior, which has not previously been measured, is suggested to be dominated by the distinctive mechanical properties of the films.