The performance of a single-chamber microbial fuel cell (MFC) using wastewater containing phenol as the anodic fuel was evaluated. The evaluation was performed considering the effects of the presence of different phenol concentrations in the anodic fuel and the external resistance at which the cells were adapted. Maximum power and current densities of 49.8 mW m(-2) and 292.8 mA m(-2) were obtained, respectively. Microbial diversity on the anode surface remained relatively stable when the phenol concentration was increased. Pseudomonas sp. was the most abundant microorganism in the MFC, followed by the genus Geobacter and Shewanella. Phenol degradation was mainly conducted by bacteria present in the wastewater, and its presence did not affect the electricity generation. The operation of the MFC with a resistance different to the adaptation resistance produced lower current and power densities; however, the variation in external resistances did not adversely affect the phenol degradation.