Real gas effects exert a significant influence on the hydraulics of natural gas transmission pipelines. In this article the implications of the selection of the equation of state for the pipeline gas flow model are investigated. A non-isothermal transient gas flow model with AGA-8 and SGERG-88 equations of state was studied. Models with Soave-Redlich-Kwong and Benedict-Webb-Rubin equations of state were solved to illustrate the overall gas flow model inaccuracies. The effect of the selection of different equations of state on the flow parameters is demonstrated and discussed. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.