Supported carbon membranes were prepared from furfuryl alcohol (FA) precursor by vapor deposition polymerization (VDP). For this purpose gamma-Al2O3/alpha-Al2O3 or glass/alpha-Al2O3 support tubes were pretreated with an acid catalyst and exposed to FA vapors at 90 degrees C. The tubes were then heated at 200 degrees C to crosslink the poly(furfuryl alcohol) (PFFA) polymer and carbonized slowly to 600 degrees C. The polymerization and carbonization cycle was repeated once to improve the permeation properties. The membranes were examined by scanning electron microscopy (SEM) and tested in a permeation cell with single gases (H-2, N-2, O-2, CO2, CH4) and with the mixture CO2-CH4. After the first polymerization/carbonization cycle the membranes had little selectivity for gas separations. After the second polymerization/carbonization cycle the membranes had ideal selectivities 10-13 for O-2:N-2, 80-90 for CO2:CH4, and 90-350 for H-2:N-2 at room temperature. The permeance was 0.6-2.5 for H-2, 0.27-0.58 for CO2 and 0.08 for O-2, all in MPU (1 MPU=10(-8) mol/m(2) Pa s). The permeances were sharply higher at 150 degrees C but the selectivities were lower, e.g. one of the membranes had H-2 permeance 10.6 MPU and H-2:N-2 ideal selectivity 30.