During the transport of natural gas through pipelines small amounts of condensate can be formed due to temperature and pressure changes. If this natural gas/condensate flow arrives at a regular, sharp-edged T-junction in the pipeline system an interesting phenomenon may be observed i.e. unequal phase splitting of gas and condensate. In this paper its has been shown that the addition of hydrogen into a natural gas stream results in a different splitting behaviour in comparison with the natural gas flow without hydrogen addition. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.