  $q$-vertex operators for quantum affine algebras have played important role
in the theory of solvable lattice models and the quantum Knizhnik-Zamolodchikov
equation. Explicit constructions of these vertex operators for most level one
modules are known for classical types except for type $C_n^{(1)}$, where the
level -1/2 have been constructed. In this paper we survey these results for the
quantum affine algebras of types $A_n^{(1)}, B_n^{(1)}, C_n^{(1)}$ and
$D_n^{(1)}$.
