  Using two flavors of maximally twisted mass fermions, we calculate the S-wave
pion-pion scattering length in the isospin I=2 channel and the P-wave pion-pion
scattering phase in the isospin I=1 channel. In the former channel, the lattice
calculations are performed at pion masses ranging from 270 MeV to 485 MeV. We
use chiral perturbation theory at next-to-leading order to extrapolate our
results. At the physical pion mass, we find m_pi a_pipi(I=2)=-0.04385(28)(38)
for the scattering length. In the latter channel, the calculation is currently
performed at a single pion mass of 391 MeV. Making use of finite size methods,
we evaluate the scattering phase in both the center of mass frame and the
moving frame. The effective range formula is employed to fit our results, from
which the rho resonance mass and decay width are evaluated.
