This paper will review some of the historic data for olefin plant feedstock in different regions of the world and the changes in feed mix. This in combination with future projections of olefins demand and availability and relative pricing of feedstock will dictate the future trends in olefin plant feedstock. This paper will also review the developments in alternative feed sources (such as methane, coal and bio) and how the economic viability of these feeds relative to conventional feed sources will impact the industry.