A graph $G=(V,E)$ is a {\it unipolar graph} if there exits a partition $V=V_1
\cup V_2$ such that, $V_1$ is a clique and $V_2$ induces the disjoint union of
cliques. The complement-closed class of {\it generalized split graphs} are
those graphs $G$ such that either $G$ {\it or} the complement of $G$ is
unipolar. Generalized split graphs are a large subclass of perfect graphs. In
fact, it has been shown that almost all $C_5$-free (and hence, almost all
perfect graphs) are generalized split graphs.