In this letter we propose the use of partial wave dispersion relations (DRs
) as the way to solve the longstanding problem of correctly incorporating e
xchange in a valid DR for electron-atom scattering. In particular, a method
is given for effectively calculating the contribution of the discontinuity
and/or Doles of the partial wave amplitude which occur in the negative E p
lane. The method is successfully tested in three cases: (i) the analyticall
y solvable exponential potential, (ii) the Hartree potential and (iii) the
S-wave exchange approximation for electron-hydrogen scattering. The latter
is the first successful DR which includes exchange.