The quantum interference pattern in the double-slit experiment is qualitatively reproduced by independent classical trajectories evolving on an effective potential obtained in the lowest order quantized Hamilton dynamics approach. The quantum effects appear due to a simple modification of the original classical potential that is sufficient to obtain a diffraction maximum in the middle between the two slits and an auxiliary diffraction structure on the sides of the central maximum. (C) 2003 Elsevier B.V. All rights reserved.