This Technical Report is an advisory State of the Art document for wet gas flow metering applications as understood in 2005. It is based on available wet gas flow metering research papers, commercial literature and practical experiences from the oil and gas industry up until the end of 2005. The operating principles apply to steady-state flows where phase change is not a dominant issue. However it should be understood that many wet gas flow metering applications could be unsteady state flows and phase change could be a dominant issue.