The filing of a reissue patent application requires identification of an error in the original patent such as claiming more or less than patentee had a right to claim. The scope of examination of a reissue patent application is more extensive than that of a reexamination. The USPTO may go beyond prior art patents and publications to address other issues of patentability as well. A patentee who survives reexamination or reissue gains enhanced prospects for litigation or licensing success.