  We examine the phenomenology of the $CP$-odd scalar $A^0$ of
two-Higgs-doublet models. We explore the parameter space determined by
triviality bounds and identify the regions where the $A^0$ can be detected at
the LHC in each of the following modes: the inclusive two-photon decay mode,
the $l^{\pm}\gamma\gamma X$ mode from $t\overline{t}A^0$ production and the
$A^0\rightarrow Zh$ channel with the subsequent decay of the $CP$-even scalar
$h$ to two photons. We find that, while the $l^{\pm}\gamma\gamma X$ mode is of
limited usefulness, the other two modes can give viable signals in fairly
large, and complementary, regions of parameter space.
