I've had some pet stains that were at least a year old in my carpet and while it didn't magically pull them completely out it did make a nice dent in the color! Plus it removed the smell of the more resent stains. I'll go back over the old stains a couple more times like it recommends with the vacuum. And I'm betting my carpets will look almost new and smell awesome too! It is a much more pleasant smell than the shout and other stain fighting products I've used.