  We report the result of our near-infrared observations (JHKs) for type II
Cepheids (including possible RV Tau stars) in galactic globular clusters. We
detected variations of 46 variables in 26 clusters (10 new discoveries in seven
clusters) and present their light curves. Their periods range from 1.2 d to
over 80 d. They show a well-defined period-luminosity relation at each
wavelength. Two type II Cepheids in NGC6441 also obey the relation if we assume
the horizontal branch stars in NGC6441 are as bright as those in metal-poor
globular clusters in spite of the high metallicity of the cluster. This result
supports the high luminosity which has been suggested for the RR Lyr variables
in this cluster. The period-luminosity relation can be reproduced using the
pulsation equation (P sqrt(rho)=Q) assuming that all the stars have the same
mass. Cluster RR Lyr variables were found to lie on an extrapolation of the
period-luminosity relation. These results provide important constraints on the
parameters of the variable stars.
  Using Two Micron All-Sky Survey (2MASS) data, we show that the type II
Cepheids in the Large Magellanic Cloud (LMC) fit our period-luminosity relation
within the expected scatter at the shorter periods. However, at long periods
($P>40$ d, i.e. in the RV Tau star range) the LMC field variables are brighter
by about one magnitude than those of similar periods in galactic globular
clusters. The long-period cluster stars also differ from both these LMC stars
and galactic field RV Tau stars in a colour-colour diagram. The reasons for
these differences are discussed.
