The latest advances in the field of zeolitic membranes for gas separation are critically reviewed with special emphasis on new synthetic protocols. After introducing the most relevant aspects to membrane performance, including adsorption trends, permeation mechanisms and support effects, we review recent achievements in membrane synthesis and discuss in detail the effect of zeolite topology and chemical composition on membrane gas separation. We pay special attention to promising 8MR high-silica structures. As the formation of defects during synthesis remains one of the major challenges for large-scale production of such membranes, we review various approaches to either limit defect formation or decrease their adverse effect by post-synthesis modification. Finally, the current challenges for this field of research are summarized and an outlook is offered on approaches to decrease fabrication costs, improve reproducibility and rational design of zeolite membranes.