The plane wave Born approximation with Coulomb, relativistic and excha
nge corrections is employed to obtain L3-shell ionization cross sectio
ns of xenon and gold bombarded by electrons and positrons in the energ
y range varying from the threshold of ionization to 100 keV. For low i
ncident energies the present electron impact cross sections are in ver
y good agreement with the available experimental data for both the tar
gets. For positron impact the agreement between the present results an
d the limited experimental data is also satisfactory. Near the thresho
ld the calculated electron impact cross sections for both the targets
can be represented by a power law over an extended energy region. The
value of the power index n agrees with the available experimental valu
e.