The structure sensitivity of the reduction of nitrate has been studied on a series of single-crystal platinum electrodes by cyclic voltammmetry and in situ FTIRAS in sulfuric and perchloric acid solutions. The nitrate reduction is a structure-sensitive reaction on single-crystal platinum electrodes. However, this structure sensitivity is essentially controlled by other species (hydrogen, sulfate) that interact strongly with the electrode surface rather than by a structure-sensitive nitrate adsorption, dissociation or reduction. Voltammetric and spectroscopic data point to adsorbed nitric oxide (NO) as the main stable intermediate of the nitrate reduction to ammonia. No evidence for the formation of N2O was found. On surfaces with sufficiently wide (1 1 1) terraces in the absence of specifically adsorbed sulfate, an oxidizable nitrate reduction product is detected voltammetrically, which may tentatively be attributed to the formation of a small amount of hydroxylamine earlier during the voltammetric scan.