Abstract: A carbon foam was prepared from petroleum mesophase pitch in a high pressure/high temperature reactor by self-bubbling of volatile gas and infiltration of nitrogen at high pressure. The carbon foam was characterized by SEM and light microscopy. It was found that temperature and pressure are important factors in determining the carbon foam structure. Higher temperature tends to enlarge pore size and increase the percentage of open porosity. Increasing pressure decreases pore apertures size and improves density. A highly regular arrangement of carbon layers along the filament can be obtained at high temperature.