  The search for charged Higgs bosons, which are predicted in supersymmetric
theories, is difficult at hadron colliders if the mass is large. In this paper
we present the theoretical set-up for the production of charged Higgs boson
pairs at the LHC in gluon-gluon collisions: $pp -> gg -> H^+ H^-$. When
established experimentally, the trilinear couplings between charged and neutral
CP-even Higgs bosons, $H^+ H^- h^0$ and $H^+ H^- H^0$, can be measured.
