  We discuss recent progress and future prospects for the analysis of the
4f${N-1}$5d excited states of lanthanide ions in host materials. Ab-initio
calculations for Ce$^{3+}$ in LiYF$_4$ are used to estimate crystal-field and
spin-orbit parameters for the 4f$^1$ and 5d$^1$ configurations. We discuss the
possibility of using excited-state absorption to probe the electronic and
geometric structure of the 4f$^{N-1}$5d excited states in more detail and we
illustrate these ideas with calculations for Yb$^{2+}$ ions in SrCl$_2$.
