  We use the worldline path integral approach to the Bern-Kosower formalism for
extending this formalism to the calculation of higher order corrections to N -
photon scattering. The case of the two-loop QED beta-function is considered in
detail. (Talk given by C. S. at the Workshop QCD 94, Montpellier, France, 7 -
13 July, 1994)
