  Substantial numbers of morphologically regular early-type (elliptical and
lenticular) galaxies contain molecular gas, and the quantities of gas are
probably sufficient to explain recent estimates of the current level of star
formation activity. This gas can also be used as a tracer of the processes that
drive the evolution of early-type galaxies. For example, in most cases the gas
is forming dynamically cold stellar disks with sizes in the range of hundreds
of pc to more than one kpc, although there is typically only 1% of the total
stellar mass currently available to form young stars. The numbers are still
small, but the molecular kinematics indicate that some of the gas probably
originated from internal stellar mass loss while some was acquired from
outside. Future studies will help to quantify the role of molecular gas
(dissipational processes) in the formation of early-type galaxies and their
evolution along the red sequence.
