  Old starburst galaxies are deficient in O stars, and hence do not exhibit
strong line emission in the optical regime. However, there remain many B stars,
which are expected to heat dust grains and generate strong continuum emission
in the far-infrared. The IRAS data for a statistically complete sample of
nearby galaxies reveal for the first time that such objects are as numerous as
30-40% of the local galaxy population.
