85 for a Category I language (Dutch, French, Italian, Portuguese, and Spanish)
90 for a Category II language (German)
95 for a Category III language (Belorussian, Czech, Greek, Hebrew, Persian, Polish, Russian, Serbian/Croatian, Slovak, Tagalog [Filipino], Thai, Turkish, Ukrainian, and Vietnamese)
100+ for a Category IV language (Arabic, Chinese, Japanese, and Korean)
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I'm with Achilles on this one, now-a-days it doesn't matter what your score is for the DLAB. You can keep your 18X contract even if you bomb it (assuming you meet all the other requirements!). Also, despite myths about not being able to study for the DLAB, there is a way... I did it!
http://usmilitary.about.com/cs/joiningup/a/dlab.htm