Microbial fuel cells are bio-electrochemical transducers that convert organic compounds (fuel) directly into electricity, through the metabolic reactions of constituent microorganisms. A distinct advantage of the technology is the ability to utilize a wide range of wastes as fuels, including human urine, the feasibility of which has already been reported [1]. The effect of urine addition in Single Chamber Microbial Fuel Cells (SCMFCs) is analyzed in the present study. Electrochemical characterization (anodic and cathodic linear sweep voltammetry (LSV), power generation and chemical oxygen demand COD degradation) was performed on SCMFCs after being fed with human urine changing the anodic solution every 1, 2 and 4 days. The SCMFCs were of 0.13 L volume with a carbon brush anode and Pt-free cathode as previously described [2] (5 cm2 geometric area). The SMFCs had been inoculated with raw wastewater for 3 weeks prior to starting the urine dosage, in order to colonize the anode with anaerobic anodophillic bacteria. The maximum power generation (85mW/m2) was recorded the day when the anaerobic feedstock was changed to urine. Contextually, a dramatic change in pH from 6-6.5 to 9 was recorded inside the cells during the day of the maximum power generation. It is assumed that this was due to the bacteria activity in breaking down urea to ammonia and CO2. The pH increase negatively affected the anodic performance and consequently the overall cell performance [3]. COD removal was different according with the retention time: 25-35% (1 day), 35-50% (2 days) and 50-60% (4 days). This is partially due to the electricity generation and partially due to the production of carbon dioxide from the urea degradation. The pH shift due to urea hydrolysis limited the performance over time, thereby strengthening the case for the microbial fuel cell technology to utilize human urine, as well as wastewater. The results underlining the necessity to control alkalinity, or to use flow condition, in order to avoid pH increase at values as higher as 9, those decreasing the performance of anode.