A Practice Note discussing ownership and assignment of patents and patent applications filed and prosecuted before the US Patent and Trademark Office (USPTO). This Note describes establishing ownership, including joint ownership, transfer of ownership, chain of title issues, and statutory and USPTO requirements for preparing and recording patent assignments. Topics include types of recorded transactions, correcting recordation errors, post-issuance recordation, establishing the assignee's right to take action in a patent application, and filing a patent application as a real party in interest without an assignment.