  Recent theoretical and observational progress has substantially improved the
definition of the lower main sequence and established a new basis for a
comparison of main sequence stars and the secondaries in CVs. The evolutionary
sequences of Kolb & Baraffe [1999] imply that the secondaries in many CVs are
expanded compared with main sequence stars of the same mass as a consequence of
unusually high mass transfer rates and/or pre-CV nuclear evolution. We show
that the location of the secondaries of all well-studied CVs in the spectral
type period diagram implies that they are consistent with having near-solar
metallicities. We show, furthermore, that the surface brightness of K/M stars
depends on gravity and metallicity and present new Barnes-Evans relations valid
for dwarfs of near-solar metallicity and the secondaries in CVs of the galactic
disk population. Distances derived by the surface brightness method agree with
recent measurements of the trigonometric parallaxes of a few selected systems.
