  Young open clusters located in the outer Galaxy provide us with an
opportunity to study star formation activity in a different environment from
the solar neighborhood. We present a UBVI and H alpha photometric study of the
young open clusters NGC 1624 and NGC 1931 that are situated toward the Galactic
anticenter. Various photometric diagrams are used to select the members of the
clusters and to determine the fundamental parameters. NGC 1624 and NGC 1931
are, on average, reddened by <E(B-V)> = 0.92 +/- 0.05 and 0.74 +/- 0.17 mag,
respectively. The properties of the reddening toward NGC 1931 indicate an
abnormal reddening law (Rv,cl = 5.2 +/- 0.3). Using the zero-age main sequence
fitting method we confirm that NGC 1624 is 6.0 +/- 0.6 kpc away from the Sun,
whereas NGC 1931 is at a distance of 2.3 +/- 0.2 kpc. The results from
isochrone fitting in the Hertzsprung-Russell diagram indicate the ages of NGC
1624 and NGC 1931 to be less than 4 Myr and 1.5 - 2.0 Myr, respectively. We
derived the initial mass function (IMF) of the clusters. The slope of the IMF
(Gamma_NGC 1624 = -2.0 +/- 0.2 and Gamma_NGC 1931 = -2.0 +/- 0.1) appears to be
steeper than that of the Salpeter/Kroupa IMF. We discuss the implication of the
derived IMF based on simple Monte-Carlo simulations and conclude that the
property of star formation in the clusters seems not to be far different from
that in the solar neighborhood.
