The potentials and possibilities offered by the rather unknown chemiluminescence-based analytical technique are discussed. Simplicity of instrumentation, low detection limits for various systems, and the inherent power of application to a vast number of natively fluorescing species or fluorophores formed after chemical derivatization broaden the scope of this relatively new detection technique. Drawbacks should be mentioned as well, amongst others limited selectivity of analysis (unless coupled to a powerful separational set-up), unexpected poor sensitivities for various analytes and the need to include an extra reaction step in the analytical procedures. Apart from the earlier gas-phase applications, the analysis in flowing streams (flow injection analysis, HPLC, and even capillary electrophoresis) has increased exponentially starting back in the early eighties. Various reagents have become available, including some originating from bioluminescent reactions (e.g. for ATP- and related analysis), not to forget the light emission as produced by diverse oxidation reactions, many of which the exact chemical pathways are not elucidated yet. On top of this, the power of chemiluminescence induction and measurements as applied to immunoassays, in the development of sensors, and, even more important, in the fast developing area of micromachining (sub-droplet-sized capillary electrophoresis) are discussed.