Large Eddy Simulations (LES) of flow around a square cylinder at ¥ § ¦ § © © are performed employing a dynamic one-equation subgrid model. An implicit fractional step method finite-volume code with second-order accuracy in space and time is used. By using a periodic boundary condition the spanwise dimension is four times the side length of the cylinder. Some global quantities, such as the dominating wake frequency (Strouhal number) and the mean and RMS values of lift and drag, are computed. Also, a series of time-and spanwise-averaged resolved velocities and turbulent stresses are provided for comparison with experiments. The influence of a finer grid on the results is investigated. Present results are in general agreement with experiments and by using a finer spatial resolution an even better agreement is found. The dynamic one-equation subgrid model is found to be stable and no sign of the numerical problems usually encountered with the standard dynamic SGS-model is observed.