A particle mesh Ewald method for calculating Coulomb interactions in three-dimensional (3D) systems with two-dimensional (2D) periodicity was developed. Computational efficiency and accuracy of this method were evaluated for a TIP3P water system with 2928 particles in a cubic box with 2D periodicity. The accuracy of this method for calculating Coulomb interactions is comparable to our previous method that uses Fourier integral. For calculations with maximum errors in the Coulomb force of 0.4-20.0 kJ mol(-1) nm(-1), the current method was up to five times faster than the previous method.