Dulles International Airport has no direct Metro service. To connect to Metro, take the Washington Flyer Express bus to the West Falls Church metro station. (Buses run every 30 minutes, and cost $8 one way / $14 round trip).
Detailed Directions on Metro.

• Stay left on exiting airport area and join Dulles Access Rd.
• Follow signs routing to I-66 East and 495.
• Continue to follow signs to I-66 East where the Access Road joins I-66.
• East for approximately 17 miles after leaving the airport.
• Via I-66 Eastbound use exit 71 (Ballston).
• Immediately after you exit, you will see a Holiday Inn on the right. Our building is located directly behind the Holiday Inn.

Washington Flyer Taxi Service:
(703) 661-6655
estimated cost: $35.00
additional person: $1.00
estimated time: approximately 30 minutes travel time

Washington Flyer Express Bus to West Falls Church Metro
1-888-WASHFLY
estimated cost: $8.00
estimated travel time: approximately 20 minutes
West Falls Church Metro to Ballston Metro
estimated cost: $1.35 peak; $1.00 off-peak; $.65 seniors/disabled
estimated travel time: approximately 7 minutes

Travelers from Dulles can get to Arlington via airport limousine (703-685-1400 or 703-471-5555) in about 30 minutes.