  We examine Lyman continuum extinction (LCE) in H II regions by comparing
infrared fluxes of 49 H II regions in the Galaxy, M31, M33, and the LMC with
estimated production rates of Lyman continuum photons. A typical fraction of
Lyman continuum photons that contribute to hydrogen ionization in the H II
regions of three spiral galaxies is $\la$ 50 %. The fraction may become smaller
as the metallicity (or dust-to-gas ratio) increases. We examine the LCE effect
on estimated star formation rates (SFR) of galaxies. The correction factor for
the Galactic dust-to-gas ratio is 2-5.
