A simple method for centering a Gaussian laser beam is proposed. It consists of partially blocking out the beam by an opaque wire; when the power of the transmitted beam is brought to a minimum, by moving the relative position of the beam and the wire, the center of the beam and that of the wire are in coincidence. By using the usual formulae for Gaussian beams, the behavior of the power variations with the relative wire-beam position, as a function of the width of the wire are analyzed. The error of the method is also analyzed and it is shown that the optimum case is when the wire diameter equals (root)2 the beam radius. We show some experimental results.