  We show that the secondaries in short-period cataclysmic variables with
orbital periods $P < 3$ hr are close to the solar-abundance main sequence
defined by single field stars. In cataclysmic variables with $P > 3$ hr, the
earliest spectral types at a given period correspond to main sequence stars,
while the majority of secondaries have later spectral types. Possible causes
are nuclear evolution prior to mass transfer and lack of thermal equilibrium
due to mass transfer. A comparison with evolutionary sequences obtained with
up--to--date stellar models implies unusually high transfer rates and a large
fraction of systems with evolved donors. There is no evidence for a secondary
of low metallicity in any of the well-studied cataclysmic variables.
