Since ejectors were first developed, research effort has been devoted to the improvement of design methods and to new applications. Ejectors can be used to pump both incompressible and compressible fluids, but the flow and mixing of compressible fluids within ejectors are difficult to analyse. This paper, in reviewing recent achievements, concentrates on ejectors for compressible fluids. In the analysis and design of ejectors, one-dimensional and two-dimensional methods are available: the one-dimensional methods provide a simple and reasonably accurate way but only limited geometrical information, whereas the two-dimensional are more accurate and they provide greater design detail; however, they are difficult to employ in design optimisation. Ejectors have a wide range of applications, among which refrigeration has a long-established history. Ejector refrigerators working on halocarbon refrigerants provide a high level of flexibility, but with the phasing-out of ozone-damaging refrigerants there is a need for research on alternatives. Ejectors can also be used in solar-powered refrigeration systems and absorption-refrigeration systems. Other newly developed applications are summarised in this paper, which presents a critical review of more than 100 published papers and is aimed at encouraging further interest among energy researchers in the study and application of ejectors.