  The BABAR collaboration measurements of the B -> pipi, B -> rhopi and B ->
rhorho decays are presented. New results, from a 113 fb-1 data sample, on the
time-dependent CP asymmetries of the longitudinally polarized component of the
B0 -> rho+rho- channel are S_{rhorho,long}=-0.19 +/- 0.33 +/- 0.11 and
C_{rhorho,long}=-0.23 +/- 0.24 +/- 0.14. Constraints on the Unitarity Triangle
angle alpha from the pipi and the rhorho systems are derived.
