Originally Posted by Jeff Wills

In general, no.

99.99% of the time, 700 means 700C (note that it's a capital "C"). For a couple years, GT offered a "700D" tire, which is now nonexistent: http://www.sheldonbrown.com/harris/tires/587.html

Read the Sheldon Brown page. Even though he's been gone for several years, the information is still quite relevant.

You're a mountain biker? Don't even get me started on the 6 different sizes of "twenty-six inch" bike tires.