U.S. courts must do more to address uncertainty about what inventions are eligible for patenting, the head of the Patent and Trademark Office said.

“The courts should take a closer look at what’s happening in this realm,” PTO Director Andrei Iancu told attorneys April 11 at the American Bar Association’s intellectual property conference.

Practitioners say a series of court decisions on patent eligibility under Section 101 of U.S. patent law have left the law poorly defined. Inventors and businesses say they’re uncertain about what inventions are patentable, and which granted patents can survive challenges.

Iancu in January introduced Section 101...