Unless I missed an errata somewhere.... The 3.5 PHB (p140) says the following, under the description for "Fighting Defensively as a Standard Action":Jerrand Redband said:Sorry to be a rules lawyer:
You cannot use combat expertise and fighting defensively in the same round unless you can perform two standard actions in a round.
This bonus stacks with the AC bonus granted by the Combat Expertise feat (page 92).
phindar said:The only thing that bugs me about Fighting Defensively + Combat Expertise is that the AC bonus you get is greater than the AC bonus you get for going Full Defense. So it you're partially defensive but still trying to attack your AC is higher than if you devote all your energy to being defensive. That's a little odd, but it's legal.