This article is from the Astronomy FAQ, by Joseph Lazio (firstname.lastname@example.org) with numerous contributions by others.
By William Keel <email@example.com>
We are on firmer ground with this one, since globular clusters are
fairly large and luminous. The only places where our census in the
Milky Way is incomplete are regions close to the galactic disk and
behind large amounts of absorbing dust, and for the fainter clusters
that are farthest from the Milky Way just now. The electronic version
of the 1981 Catalogue of Star Clusters and Associations. II. Globular
Clusters by J. Ruprecht, B. Balazs, and R.E. White lists 137 globular
clusters in and around the Milky Way. More recent discoveries have
added a handful, especially in the heavily reddened regions in the
inner Galaxy. As a rough estimate accounting for the regions that
cannot yet be searched adequately, our galaxy should have perhaps 200
total globulars, compared with the approximately 250 actually found
for the larger and brighter Andromeda galaxy.