The objective of this paper is to review linear generator systems for wave energy conversion and the research issues related to this. The paper starts with a short review of wave energy conversion, indicating that the different wave energy conversion systems that have been presented in literature have very different generator systems. Next, a few state-of-the-art linear generator systems are discussed, such as the linear generator of the Archimedes Wave Swing (AWS) and the linear generator developed in Uppsala. Subsequently, some remaining problems and possible solutions that need further research are listed. The paper concludes with some sensible directions for further research, such as investigating an increase of the speed of the linear motion of the wave energy converter, investigating other generator types with higher force densities and possibly better efficiencies (for example, transverse flux permanent magnet machines) and investigating generator constructions that result in cheaper generators.