A modification of the Ewald type summation of the dipole-dipole interactions in computer simulation of a system periodic in two directions is presented. Using Fourier transforms of the functions appearing in the reciprocal-space term the energy expression has a simple form, which is similar to that in the conventional three-dimensional Ewald method. The modified method is applied in the molecular dynamics simulations of two systems composed of polar ellipsoidal particles, and it is much faster than the traditional two-dimensional Ewald method. (C) 2002 Elsevier Science B.V. All rights reserved.