When you display style lists, you can choose to display only those actually
used in the document. The setting is provided differently according to which
version of Word you have, but it's there at least since Word 2000 (might be
there for prior versions also, but my memory isn't good enough).

You can delete styles in bulk using the Organizer, but you need to know
which ones to delete. You can print a list of the styles by printing the
document, selecting Styles from the Print What drop down on the Print
dialog. So if you're really keen, print the full list of styles, then select
'Styles in use' from the formatting dialog, mark off what's now shown in the
Styles list, and delete the rest.

You can also search for, and replace, styles using Find and Replace.

I got this from an issue of Editorium Update.

Use at your own risk.

===================================================

Sub DeleteUnusedStyles()
'Courtesy of the Editorium
'www.editorium.com
Dim sty As Style
For Each sty In ActiveDocument.Styles
If sty.BuiltIn = False Then
If sty.InUse = False Then
   sty.Delete
Else
   Selection.HomeKey Unit:=wdStory
   Selection.Find.ClearFormatting
   Selection.Find.Style = ActiveDocument.Styles(sty)
   With Selection.Find
       .Text = ""
       .Replacement.Text = ""
       .Forward = True
       .Wrap = wdFindStop
       .Format = True
       .MatchCase = False
       .MatchWholeWord = False
       .MatchWildcards = False
       .MatchSoundsLike = False
       .MatchAllWordForms = False
   End With
   Selection.Find.Execute
   If Selection.Find.Found = False Then sty.Delete
End If
End If
Next sty
Selection.HomeKey Unit:=wdStory
End Sub

Thanks to all of you for the help!

Klaus