  C-odd asymmetry can be studied from an accurate measurement of the angular
distribution due to the interference between the S- and P-waves in e+e- --> pi+
pi- at order alpha^3. The asymmetry is dominated by the pion rescattering
diagram which is enhanced by the presence of the ln(s/m^2_e), and is quite
large (10% at theta=30^0 and sqrt{s} < M_{f_2}) compared to alpha/pi=0.3%. This
process can also be used for alternatively measuring the size of the
rescattering term and the phase of the S-wave amplitude, but does not help to
solve the present discrepancy between the hadronic spectral functions from e+e-
and tau-decay data.
