This is the twentieth of Workshops in Particle Physics being held yearly at the Planibel Hotel of La Thuile, Aosta Valley. La Thuile is a beautiful mountain village located 1450 m a.sl., about 40 km north of the city of Aosta, on the road to the Mont Blanc. The hotel is at the bottom of a vast skiing area connected with the French ski resort La Rosiere and it is an outstanding complex for winter sports and congresses. The Rencontres will bring together about 120 active experimentalists and theorists to review the status and the future prospects in elementary particle physics. A special session will be devoted to the impact of Science on Society.