Impact milling is investigated as a rapid, one-step, solvent free, ambient temperature method to make high capacitance porous graphitic materials from natural flake graphite. The effects of impact milling-induced structural and chemical changes on the capacitance of the graphitic material are evaluated in aqueous electrolyte (1 M H2SO4). Gas adsorption analysis shows that the surface area of the graphite increases from 8 to 350 m(2)g(-1) after 6 hours of milling. The increase in surface area is accompanied by an increase in pore volume to 0.36 cm(3)g(-1). Mesopores account for 75 % of the pore volume. Scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy show that impact milling creates fractured material with fewer layers and less sp(2) hybridized carbon than natural flake graphite. In cyclic voltammetry and electrochemical impedance spectroscopy, the impact-milled porous graphitic material displays near ideal capacitive behavior and low resistance. Galvanostatic charge/discharge shows that the milled porous graphite has gravimetric and area normalized capacitances of 55 Fg(-1) and 16 mu Fcm(-2), respectively. Taken together, the electrochemical and structural data show that solvent free, ambient temperature impact milling is a viable single-step method to create cost competitive porous graphitic material with high capacitance.