The preparation of a mesoporous carbon was attempted by a steam activation of a mixture of coal and metal acetylacetonate at 900 degrees C. The resultant porosity of the activated carbon was influenced more by the type of acetylacetonate [Al(acac)(3), Y(acac)(3), TiO(acac)(2), or Zr(acac)(4))] than by the rank of the coal (Miike, Taiheiyo, and Morwell). Samples obtained from TiO(acac)(2) showed a particularly high mesoporosity even at an early stage of activation, as evaluated by the BET and BJH analysis of the N-2 adsorption isotherm. To clarify the influence of TiO(acac)(2) on the mechanism of formation of a remarkable amount of mesopores, the structure of the activated carbon derived from the Ti complex was investigated by X-ray diffraction measurements and observations with a transmission electron microscope (TEM). The carbon matrix was composed of small graphite-like crystallites with mesopores and TiO2 (rutile and brookite) particles dispersed homogeneously throughout the whole matrix. The shape of the characteristic mesopores resembled that of the TiO2 particles. The particle size distribution determined by image analysis of a TEM photograph quantitatively shows the similarities in the average size of TiO2 particles and pores. It is believed that the formation of mesoporosity in the activated carbon is closely related to the migration of TiO2 from the carbon matrix.