Atheism is the logical conclusion of Agnosticism. If you don't believe me please read on.
There is a common misconception that an Agnostic is someone who cannot decide what to believe - or they don't believe in anything. An Agnostic is technically someone who believes that God cannot be proven to exist, nor can God be disproven to exist, given our present knowledge. A basic argument an agnostic would use is that you cannot deduce that God exists from logic alone. eg the ontological, cosmological, transcendental, teleological, argument from morals, argument from miracles, argument from scripture, argument from personal experience are all flawed (elaborations on these flaws abound, just google them). And as long as God doesn't come down and introduce himself there is no way to prove he exists. In addition, there's no way to prove that practically ANYTHING doesn't exist. For example, you can't prove there isn't a Flying Spaghetti Monster, a Zeus, a Flyping Purple People Eater, or a Bigfoot. Therefore an Agnostic is not on the fence about God - an Agnostic KNOWS that there is currently no way to prove or disprove God(s). This is the definition of Agnostic.
Given that there is no evidence for the Flying Spaghetti Monster, Zeus, a Flying Purple People Eater, Bigfoot, or God(s) the rational conclusion is that until proven otherwise they do not exist. The idea that the burden of proof is on the believer bridges the gap from Agnosticism to Atheism.
Unlike propaganda claims, an Atheist does not mean someone hates God and is immoral. Atheism literally means "without Theism". An Atheist is someone who simply does not believe in God(s). It's does not automatically mean that an Atheist disbelieves in God in a definite sense (although she might).
If an Agnostic is a logical person, she knows that you cannot prove or disprove a God just like unicorns and Zeus. The logical conclusion is disbelief until evidence presents itself to support a belief. Therefore, an Agnostic is without Theism and is an Atheist.