  We undertook a long term project, DIRECT, to obtain the direct distances to
two important galaxies in the cosmological distance ladder -- M31 and M33 --
using detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult
to detect, DEBs provide us with the potential to determine these distances with
an accuracy better than 5%. The extensive photometry obtained in order to
detect DEBs provides us with good light curves for the Cepheid variables. These
are essential to the parallel project to derive direct Baade-Wesselink
distances to Cepheids in M31 and M33. For both Cepheids and eclipsing binaries,
the distance estimates will be free of any intermediate steps.
  As a first step in the DIRECT project, between September 1996 and October
1997 we obtained 95 full/partial nights on the F. L. Whipple Observatory 1.2 m
telescope and 36 full nights on the Michigan-Dartmouth-MIT 1.3 m telescope to
search for DEBs and new Cepheids in the M31 and M33 galaxies. In this paper,
fourth in the series, we present the catalog of variable stars, most of them
newly detected, found in the field M31D $[(\alpha,\delta)= (11.\arcdeg03,
41.\arcdeg27), J2000.0]$. We have found 71 variable stars: 5 eclipsing
binaries, 38 Cepheids and 28 other periodic, possible long period or
non-periodic variables. The catalog of variables, as well as their photometry
and finding charts, is available via anonymous ftp and the World Wide Web. The
complete set of the CCD frames is available upon request.
