The electrochemical behaviour of Pt(100) electrodes immersed in semicarbazide containing acidic solutions has been studied by means of cyclic voltammetry and in situ FTIR spectroscopy. Various adsorbed and solution intermediates have been detected spectroscopically in the potential range between 0.10 and 1.20 V RHE. Adsorbed CO, both linearly-and bridge-bonded, is formed upon the dissociative adsorption of semicarbazide for potentials above 0.25 V RHE. This seems to be the main path for the oxidation of semicarbazide to CO2 and molecular nitrogen. Other reaction paths involve the formation of urea and nitric oxide. These species have been detected in the adsorbed state for potentials between 0.50 and 0.90 V. The in situ infrared spectra also show bands in the C=N stretching region which have been tentatively assigned to the formation of cyanamide and adsorbed cyanate anions.