The roughness and microporosity of platinum thin-film electrodes, which act as transducers in electrochemical biosensors, have been varied by evaporating titanium or aluminum as top layers and subsequent annealing and etching of these metal films. This defined structural variation is very important in the field of chemo- and biosensors. The electrochemical characteristics of the electrode surface were investigated by cyclic voltammetry in 0.5 M H2SO4. From this the real electrode area was determined by calculating the charge density in the hydrogen adsorption and desorption regions, and the roughness factor, defined as the ratio between the calculated charge density and the theoretical value of smooth polycrystalline platinum, covered a range from 1.1 to 8.85. The platinum surface was studied by cyclic voltammetry, laser-secondary-neutral-mass-spectroscopy and atomic force microscopy.