Ultrathin layers of a new metallosupramolecular iron(II) coordination-polyelectrolyte containing 1,4-bis(2,2':6',2"-terpyridine-4'-yl)benzene (1) have been prepared by alternating adsorption from dilute solution, Adsorption on oppositely charged surfaces and layer-by-layer growth were investigated in situ by sc-face plasmon resonance spectroscopy. The average film thickness of coordination-polyelectrolyte 1 is 18 Angstrom and is in good agreement with a molecular layer. Water can penetrate the film resulting in an increased film thickness. Adsorption kinetics show two distinct regions., Adsorption is a diffusion-controlled transport process obeying a root t dependence at the beginning of adsorption, Once a certain amount is adsorbed, adsorption can be described by a first-order rate law. Another minor rise id reflectance at high surface coverages is attributed to additional insertion of metal ion-ligand units into the metallosupramolecular coordination-polyelectrolyte layer.