These studies were conducted to determine the effects of various concentrations of ammonium and nitrate on current generation using dual-cathode microbial fuel cells (MFCs). Current generation was not affected by ammonium up to $51.8{pm}0.0$ mg/l, whereas $103.5{pm}0.0$ mg/l ammonium chloride reduced the current slightly. On the other hand, when $60.0{pm}0.0$ and $123.3{pm}0.1$ mg/l nitrate were supplied, the current was decreased from $10.23{pm}0.07$ mA to $3.20{pm}0.24$ and $0.20{pm}0.01$ mA, respectively. Nitrate did not seem to serve as a fuel for current generation in these studies. At this time, COD and nitrate removal were increased except at $123{pm}0.1$ mg ${NO_3}^-/l$. These results show that proper management of ammonium and nitrate is very important for increasing the current in a microbial fuel cell.