A process for the preparation of an olefinic product in the presence of a catalyst comprising an aluminosilicate having one-dimensional 10-membered ring channels and a silica-to-alumina-ratio of less than 170, and at least one Group IB metal at a metal loading of between 0.1 and 10 wt % of the aluminosilicate, the process comprising reacting an oxygenate feedstock under oxygenate conversion conditions to produce a reaction, product comprising ethylene and/or propylene. An oxygenate conversion catalyst is also claimed.