Compilations tag recognizable in iTunes?

Is there a way of creating a compilations tag which iTunes will recognize?
I want to edit all my compilation albums at once (I have a lot!) and then import them into iTunes so they automatically remain in the correct album.
If I import them as they are, each album has one track per artist and I have to edit them one by one in iTunes which will take forever.
Thanks in advance for any help.

But then you have left out the field ALBUMARTIST. You should fill that with "Various Artists" or something like that. This then should lead to the correct grouping.
If you want to use the additional feature that iTunes groups compilations under the dummy entry "Compilation" proceed as follows in MP3tag:

Load all files for compilations
Select all loaded files
Press Alt-T to open "Extended tags" dialogue.
Click on "New" button
Select "Compilation" as field name.
Enter "1" as value.
Click on OK until the dialogues are closed.
THis will save new field.
Now you only have to get iTunes to update the database.

Thanks so much this is exactly what I was looking for.
I am still not satisfied with iTunes though. It is ridiculous that it doesn't auto-update.
I work with 4 different iPods for various shows though, so completely switching to another media player is not an option.
I used to use Creative Media Source in the days where I had a Zen, it is the best player (for MP3s) and organiser I ever used.
Shame it's no longer available.
Thanks again.