Color reconnection and Bose-Einstein correlations in W pair events at LEP

Interference effects between the products of hadronically decaying W bosons can affect the ultimate precision of the W mass measurement at LEP II. Interference effects include colour rearrangement between colour singlets from the two W primary branching, gluon exchange during the parton cascade, and mixing of identical pions due to Bose- Einstein correlations. The status of the experimental study of such effects, based on data collected at LEP in 1996 and 1997, is reviewed in this report. (13 refs).