How significant must unexpected properties be to overcome obviousness?

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.

For unexpected properties to overcome an obviousness rejection, they must be shown to have a significance equal to or greater than the expected properties. The MPEP provides guidance on this:

“Where the unexpected properties of a claimed invention are not shown to have a significance equal to or greater than the expected properties, the evidence of unexpected properties may not be sufficient to rebut the evidence of obviousness.” (MPEP 716.02(c))

This means that applicants must not only demonstrate unexpected results but also show that these results are significant enough to outweigh the expected benefits or properties of the invention.