AbstractGraphite intercalation compounds are of considerable scientific interest for both applied and fundametal reasons (structural ordering). Micro Raman spectroscopy has been used to investigate graphites intercalated with sulphur trioxide. In these compounds, theE2g2vibrational layer mode of the graphite lattice shows the known linear frequency dependence with the inverse of the step as observed for many acceptor‐type intercalates. The frequency behaviour of this mode is also indicative of a difference between intercalated graphites prepared with either liquid or gaseous SO3. A study of the Raman spectra as a function of time allowed information on the intercalation kinetics and the ageing of these materials to be obtaine