There are a few different Atkins bars, and the amount of carbs in each one varies.  The original Atkins bar has 12 grams of carbs, while the Advantage line of bars ranges from 3-7 grams of carbs per bar.  The Endulge line of bars, which are meant to be more like dessert, have 8-10 grams of carbs each. So, if you're looking for the Atkins bar with the lowest carbs, you'll want to choose from the Advantage line.