Environmental monitoring is of great importance for its protection. Biosensors based on a combination of a biological sensing element and an electronic signal-transducing element that offer high selectivity, high sensitivity, short-response time, portability and low cost, are ideal for monitoring pollutants in aquatic environments, such as rivers or drinking water. In this presentation, I will review our research work on the development of enzyme-, microbial- and antibody–based biosensors for monitoring chemical pollutants such as pesticides and heavy metals and biological pollutants such as toxins, viruses and bacteria.