Bioluminescence means production of light by living organisms like microorganisms. Among microbes luminous bacteria are the most abundant and widely distributed in marine, terrestrial and freshwater environment. The process of bioluminescence involves production of pigment luciferin and the enzyme involved is luciferase which is responsible for the reaction. In present days risk of pollution is usually determined by the total concentration of pollutant present in particular samples like soil, water and sediments. Bioluminescence can be used for detection of pollutant like pesticides and the some of the bacterial species tested includes Vibrio fischeri, Vibrio harveyi and Pseudomonas fluorescens. Natural or genetically modified bacteria can be used for preparation of biosensor probes which helps in screening and detection of toxicity. The main principal involved behind this is very simple; in case of optimal condition the bacteria emit light normally but in presence of toxic substances their luminescence decreases. Thus presence of toxic molecules can be evaluated. This is very rapid, sensitive, reproducible and cost effective assay for detection of pollutants.