Fourier-transform infrared spectroscopy has been applied to study the adsorption and deuteration of perdeuteroethene (C2D4) at 298 K on a deuterium-exchanged Pt/SiO2 catalyst. The spectra show absorptions associated with pi- and di-sigma-bonded (C2D4) and with (CCD3), and a trace of (CCD2H), ethylidyne surface species. These were identified by comparison with the closely-corresponding pattern of absorptions from the adsorption of C2H4. They are also correlated with previous spectroscopic results from C2D4 adsorption on Pt single-crystals and from analogous ligands in organometallic compounds. Deuteration of the initially-adsorbed species gives only gas-phase C2D6 and a trace of C2D5H.