Microbial fuel cells (MFCs) and biohydrogen production represent new approaches to bioenergy production and wastewater treatment. We have shown that it is possible to directly generate electricity from organic matter using bacteria as a biocatalyst in a MFC. To produce current, bacteria transfer electrons obtained from the oxidation of organic matter to an electrode under anaerobic conditions. The electrons flow to the counter electrode (cathode) where they combine with oxygen and protons (from the anaerobic chamber) to form water. Using glucose, we can produce 500 to 1000 mW/m2 (based on anode surface area). With domestic wastewater, we have shown it is possible to generate power at 10 to 150 mW/m2 while achieving wastewater treatment (80% removal of the biochemical oxygen demand of the wastewater). Although these power densities appear low, it should be sufficient to make energy recovery from wastewater economically feasible in the near future due to the high surface areas currently used in some wastewater treatment plants. Using MFCs to treat the effluent from fermentation reactors also shows great promise for making biohydrogen production viable. Bacteria can be used to make hydrogen gas via fermentation reactions that is 60% hydrogen gas (40% CO2). The main soluble products from biohydrogen production are acetic and butyric acids. In our MFC tests we have achieved maximum power densities of 500 mW/m2 with acetate and 300 mW/m2 using butyrate. These findings show that it is possible to recover bioenergy from domestic and industrial wastewaters; further development of these technologies could lead to wastewater treatment processes that are net energy producers rather than consumers.