Results are reported for the one-component permeation of a number of gases through a silicalite-1 membrane. The effect of several operating conditions, like the temperature, the feed pressure, the sweep gas flow rate, and the orientation of the membrane, on the flux are discussed. The optimal experimental conditions are identified for both steady state and transient permeation. Results for the flux as function of the pressure, 10–900 kPa, and as function of the temperature, 200–700 K, are modelled taking two diffusion mechanisms into account. Permeation results are reported for two different silicalite-1 membranes. A small difference in the permeance is observed, indicating a high reproducibility of the zeolite membrane synthesis. The contribution of the equilibrium isotherm to the flux and the permeance is demonstrated. A comparison is made between results obtain with helium and argon as the sweep gas. Finally, results are reported for the permeation of pure gases through a silicalite-1 membrane modified by silanation.