[eitland]

Where I live McDonalds are the only fast food chain to hammer the fact that their burgers are 100% pure beef (produced inside the borders of my country even).

Don't know if it is correct but repeating it on tv for months sounds risky if they are lying.

[vidarh]

It is correct some places, and may now finally be correct everywhere, but especially in the US it is not all that obvious whether or not your meat is "pure" in any meaningful sense:

http://en.wikipedia.org/wiki/Pink_slime

[mseebach]

I assume that what the GP referred to is that even though it's all "beef" (part of a cow's body), one beef product might be mostly tendons, bonemeal and fat, while another is a cut of fillet, almost 100% muscle tissue. Colloquially, I think most people would agree that the latter is more pure than the former.