Publishers Weekly reports Amazon sold about 6 million Kindle Fires in the fourth quarter of the year - that's the three-month period that ended Dec. 31, 2011.
Stifel Nicolaus analyst Jordan Rohan credits Amazon's competitive pricing for the success of the Android-based tablet.
The Kindle Fire sells for $199. The least expensive Apple iPad 2 costs about $499.
"Kindle Fire has staked out an important market position due to its loyal Amazon customer base and attractive device pricing," said Rohan.
The Kindle Fire remains the top-seller in Amazon's electronics category.