We've taken a taxi in Paris very late, but does anyone know how early they start running? We need to be at the Gare du Nord by 6:45 AM, but we're hesitant to book tickets on the eurostar quite that early unless we're sure we can get to Gare du Nord in time.

Best,
Sandy

I read they have a night rate called Tarif B (7 p.m. to 7 a.m.) in addition to a day rate (Tarif A from 7 a.m. to 7 p.m.) so I guess they run 24 hours.

That is correct.

http://www.parisby.com/transpor/taxi.htm

I think the info about extra charge is correct. Ask your hotel to reserve a taxi the day before for the time you want.

You can get cabs any time of day or night in Paris. The metro and some bus lines will also be running (they start around 5.30 am)

I agree on the suggestion to have the hotel book for you. I have four kids and we almost always need two taxis to travel from a hotel to train station/airport. Hoping that taxis will majically appear is no fun early in the morning! Just remember to call down to the front desk 20-30 minutes before you want to leave to make sure some one has called!