A blogger with WAY too much time on his hands has put together a fascinating, comprehensive breakdown on the sex lives of the characters on "Friends".

To do it, he "thoroughly researched" all 236 episodes, which spanned 10 seasons...by watching them, reading the outlines of each episode, and reviewing the lists of guest stars. He only counted the main characters' sexual escapades with partners that actually appeared on the show, not the ones that the characters mentioned as having happened in the past.
Here's the breakdown, along with the percentage that actually spawned "serious relationships."
-Joey (MATT LEBLANC):17 sexual partners...four, or 23.5%, led to serious relationships.
-Phoebe (LISA KUDROW): 16 sexual partners...six, or 37.5%, led to serious relationships.
-Ross (DAVID SCHWIMMER): 16 sexual partners...eight, or 50%, led to serious relationships.
-Rachel (JENNIFER ANISTON): 14 sexual partners...ten, or 71.4%, led to serious relationships.
-Monica (COURTENEY COX): 13 sexual partners...five, or 38.5%, led to serious relationships.
-Chandler (MATTHEW PERRY): 9 sexual partners...three, or 33.3%, led to serious relationships.