Interpreting CP Asymmetries in B->pi+ pi- Decays

We discuss methods used to interpret the measurements of CP-asymmetry in B->pi+pi- within the framework of the Standard Model. Interpretations using various theoretical inputs are given, ranging from the rather general, yet unpredictive, properties based on strong isospin symmetry to highly predictive calculations using QCD Factorization. The calculations are performed using the software package CKMFitter and a frequentist method, Rfit.