Measurement of sin2β in Tree Dominated B0 Decays and Ambiguity Removal

The most recent results from the B-factories on the time-dependent CP asymmetries measured in B0-decays mediated by quark-transitions are reviewed. The Standard Model interpretation of the results in terms of the parameter sin2β leads to a four-fold ambiguity on the unitarity triangle β which can be reduced to a two-fold ambiguity by measuring the sign of the parameter cos2β. The results on cos2β obtained so far are reviewed.