  A significant number of S0 galaxies with a detectable ISM show some level of
on-going massive-star formation activity in the form of visible HII regions. A
rich ISM, however, does not guarantee star formation: a similar number of
gas-rich S0s have no detectable HII regions down to the level of regions
ionized by single O stars. The H-alpha luminosities of star-forming S0s imply
global star formation rates as much as 2-3 orders of magnitude lower than in
spirals. Spectroscopy of the bright HII regions in the six star-forming S0s
studied thus far reveal solar gas-phase oxygen abundances. In general, S0s
follow the general trends of O/H with galaxy luminosity and Hubble Type seen
for Spirals and Irregulars, and have O/H abundances typical of spirals of
similar total stellar luminosity. The implications are that S0s are the low end
of the Hubble Sequence of Spirals, and that their ISMs are primarily internal
in origin. The surprise is that two counter-rotating S0s, which show direct
evidence of a massive infall of gas and stars, also follow these trends.
