The rarefied gas flow through a short channel into a vacuum has been investigated computationally using the direct simulation Monte Carlo method. Taking into account the gas-surface scattering and the gas molecule-molecule interaction, the mass flow rate is calculated as a function of gas rarefaction and the length to height ratio. This study demonstrates that the effects of the gas molecule-molecule interaction and the gas-surface scattering can make a noticeable impact on the mass flow rate of the rarefied gas through a short channel into a vacuum. The maximum manifestation of these effects was evaluated. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3504596]