Among the many methods reported for toxics compound detection, chromatographic methods such as HPLC and GC are often used as reference methods. Despite their high sensitivities, these techniques are expensive, time-consuming and require highly trained personnel, furthermore they are not adapted for in situ and real time detection of pollutants. At the same time, they are not able to give any information concerning the toxicity of the sample. Biochemical sensors appear as a reliable alternative to these classical methods for the rapid and simple detection of toxics compounds. Over the last decades, bio-tools have emerged as an ultra sensitive and rapid technique for detection of chemical and biological components in environmental monitoring, food and quality control. A successful biosensor for toxicity monitoring should offer comparable or even better analytical performances than the traditional chromatographic systems. Ideally, such sensors should be small, cheap, simple to handle and able to provide reliable information in real time without or with a minimum sample preparation. This special issue will highlight the innovative researches carried out in the development of biosensors/bioassays for the determination of pollutants and toxic compounds especially in water and food samples.