Radioactive labeling and infrared spectroscopy are frequently used as direct, in situ probes into the structure of the electrochemiacl solid/liquid interface. These techniques are compared, in a polemical fashion, in the context of a recent publication by Parry et al. (Langmuir 1993, 9, 1878) where the research potential of the former technique was not adequately depicted. It is shown below that radiotracers can clearly differentiate between the surface and solution species, both neutrals and anions. In addition to the surface specificity, the radiotracers offer a quantitative determination of adsorbate surface concentrations, a feature not yet demonstrated with surface infrared spectroscopy in electrochemistry. Therefore, these two techniques are complementary. Examples of the combined radiochemical and spectroscopic measurements of adsorption with equivalent (smooth) electrode surfaces are quoted.