When should prior art figures be included in a patent application?

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.

Generally, prior art figures are discouraged in patent applications. As stated in MPEP 608.02(g), Figures showing the prior art are usually unnecessary and should be canceled. This principle is based on the decision in Ex parte Elliott, 1904 C.D. 103, 109 OG 1337 (Comm’r Pat. 1904).

However, there are exceptions to this rule. The MPEP states that prior art figures may be retained where needed to understand applicant’s invention. In such cases, these figures must be clearly labeled as prior art.