Additive Manufacturing, or 3D printing, is moving from the research labs and into both consumer and commercial manufacturing markets. As the systems, processes and materials available are becoming more mature we are seeing them being tested for new application areas such as electronics. In this paper we review how fused deposition modelling (FDM) is being explored for creating microwave circuits and componentry, their RF performance and the materials challenges faced. In recent years such microwave circuits and components have included antennas, lenses, anti-reflective coatings, transmission lines and planar circuits, waveguide terminations, performing at frequencies ranging from low GHz up to tens of GHz. Additive manufacture of such objects allows new, novel and complex structures to be fabricated with lower impact on the environment relative to current manufacturing processes, plus the rapid prototyping of circuits. Additionally it currently offers reasonable RF performance that can be competitive through further advances in manufacturing processes and materials.