Choose one weapon group for which you have already selected Weapon Focus.
Prerequisites
Base attack bonus +8, proficiency with selected weapon group, Weapon Focus with selected weapon group.
Benefit
You gain a +1 bonus on all attack rolls and a +2 bonus on all damage rolls you make using weapons from the selected weapon group. This stacks with other bonuses on attack and damage rolls, including the ones from Weapon Focus.
Special
You can gain Greater Weapon Focus multiple times. Its effects do not stack. Each time you take the feat, it applies to a new weapon group.