What is the “Old Combination” principle in patent law?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

The “Old Combination” principle was a former doctrine in patent law that suggested an inventor who improved only one element of an old combination should not be able to patent the entire combination. However, this principle is no longer valid in modern patent law.

As stated in MPEP 2173.05(j): “A CLAIM SHOULD NOT BE REJECTED ON THE GROUND OF OLD COMBINATION. With the passage of the 1952 Patent Act, the courts and the Board have taken the view that a rejection based on the principle of old combination is NO LONGER VALID.”