Self-assembly of oligo(ethylene glycol)-terminated and amide group containing alkanethiols (HS(CH2)(15)CONH-EG(n); n = 1, 2, 4, 6) on gold are investigated by contact angle goniometry, ellipsometry, and infrared reflection-absorption spectroscopy. The compounds are shown to form highly ordered monolayers. The molecular conformation of the oligo(ethylene glycol) sublayer is found to depend on the oligomer chain length and intermolecular interactions within the layer, as evidenced by a sharp increase in the amount of helical conformers for n = 6.