  A possible SU(15) process at HERA is investigated. The process that we
consider is $e^- P\ra \bar\nu_e \mu^- \mu^- +anything$ through the exchange of
new heavy gauge bosons $X^-$ and $X^{--}$ which are predicted in SU(15). This
process produces two easily observable like-sign muons in the final state. The
cross section of this process is calculated by using HELAS and VEGAS programs,
and PDF-library functions. The cross section turns out to be small to be
observed in near future.
