  The observed masses, radii and temperatures of 60 medium- to long-period
binaries, most of which contain a cool, evolved star and a hotter less-evolved
one, are compared with theoretical models which include (a) core convective
overshooting, (b)mass loss, possibly driven by dynamo action as in RS CVn
binaries, and (c) tidal friction, including its effect on orbital period
through magnetic braking. A reasonable fit is found in about 42 cases, but in
11 other cases the primaries appear to have lost either more mass or less mass
than the models predict, and in 4 others the orbit is predicted to be either
more or less circular than observed. Of the remaining 3 systems, two ($\gamma$
Per and HR 8242) have a markedly `over-evolved' secondary, our explanation
being that the primary component is the merged remnant of a former short-period
sub-binary in a former triple system. The last system (V695 Cyg) defies any
agreement at present. Mention is also made of three other systems (V643 Ori, OW
Gem and V453 Cep), which are relevant to our discussion.
