Intercalation of AlCl3 into HOPG was carried out from a liquid phase in the presence of additives. The data of elemental analysis and the observation by XRD showed that the ability of halogens to support the preparation increases in the order iodine<bromine<chlorine. The order is explained on the basis of the difference in the electronegativity of halogens. When CrO3 is used as the additive, the extent of AlCl3 intercalation is negligible. On the other hand, AlCl3 was intercalated into graphite, in which a relatively small amount of CrO3 was intercalated in advance. The same behaviour of AlCl3 and CrO3 was observed during the intercalation from a vapour phase. The intercalation of AlCl3 was anticipated to be induced by the appearance of positively charged graphite layers and CrO3delta- molecules near the edges of graphite flakes.