  Evidence on the ages and masses of Mira variables is reviewed. Period
increases with increasing initial mass. Miras of logP about 3.0 have initial
masses of near 4 solar masses. It is suggestd that the apparent gap in the LMC
PL relation at about this period may be due to the onset of hot bottom burning
and that this adds about 15 to 20 percent to the stellar energy production.
Shorter period HBB stars are probably overtone pulsators. T Lep may be an
example of cool bottom processing.
