This review describes the principle and applications of bioluminescent enzymatic toxicity bioassays. This type of assays uses bacterial coupled enzyme systems: NADH:FMN-oxidoreductase and luciferase to replace living organisms in developing cost-competitive biosensors for environmental, medical and industrial applications. These biosensors instantly signal chemical and biological hazards and allow for detecting a great amount of toxic compounds with advantages associated with fast results, high sensitivity, simplicity, low cost and safety of the procedure.