An active oxide film has been produced on the inner surface of capillary aluminum tubing, rendering the material suitable for gas-solid capillary chromatography. The separating efficiency of the oxide-coated aluminum tubing is comparable to that obtained with liquid-coated capillary tubing. Order of elution of olefins and paraffins is comparable to that experienced with granular activated alumina, but retentivity toward olefins and aromatics is much greater. Means of reducing the activity of the oxide film are discussed, as well as advantages and potentialities of the capillary column, which can be operated at temperatures of at least 500°C.