Bose-Einstein Correlations at Lep

Bose-Einstein Correlations are studied since a long time in high energy physics, but are still poorly understood. As this effect can be a source of large systematic error in W mass measurement in the W -> q_{1bar {q_2}q_3bar {q_4}} channel, new studies are made by the four LEP experiments, both using the Z peak data (from LEP1) and the W pairs data (from LEP2). Also, looking at these correlations in W pair events gives an insight on the simultaneous hadronization of two color strings. The analyses performed by the four LEP Collaborations are presented. In the WW -> q_{1bar {q_2}q_3bar {q_4}} channel, a consistent picture of no correlations between the decay products of the two W's seems to emerge.