Ultrafine carbon cryogel (UCC) microspheres of diameter < 5 mu m with desirable mesopores were successfully synthesized using a homogenizer during the inverse emulsion polymerization of a resorcinol-formaldehyde (RF) aqueous solution in an organic solvent as a continuous phase (CP) containing nonionic surfactant, SPAN80 as an emulsifier, followed by solvent exchange, freeze-drying, and pyrolysis in an Ar atmosphere. The curing time of RF solution before emulsification is a significant factor in controlling the size of the microspheres without changing their porosity. Both the mesoporosity and the size of the microspheres decreased on increasing SPAN80 and RF solution concentration in an inverse emulsion, which showed the possibility of controlling the mesoporosity and the Size of the UCC microspheres. Furthermore, hexane could also be used as the continuous phase in the emulsion polymerization. The mean diameter of the UCC microspheres increased and their mesopore volume decreased with increasing pyrolysis temperature. (c) 2006 American Institute of Chemical Engineers.