PROVISIONAL PATENT APPLICATIONS: Use and Abuse is the completion of a four-book series on the topic of quality in patents and patent portfolios. This book describes a provisional patent application (PPA), shows how it differs from an ordinary non-provisional application (NPA), and explains how it can provide an early priority date for later applications and patents. There are few formal requirements for a PPA, which can be good in that it gives freedom to explain an invention in the inventor’s own words, but can also be bad in that the application often fails to explain the invention clearly and comprehensively. Critically important is that the PPA present and define the “key claim terms” (KCTs) that will later be used in the claims of an ordinary patent application and a resulting patent. If a PPA defines these terms and explains the invention well, it is a “good” application. If it does not, then it is a “bad application.” The book includes four chapters. • First, a discussion of the provisional application generally, including its advantages and disadvantages relative to a non-provisional application. • Second, four specific cases of very good PPAs, which create a model against which other PPAs may be judged. Each case includes an introduction, a statement of what happened, and a summary in the form of Lessons Learned from that case. • Third, nine cases of bad PPAs, in which all legal protection is lost, or in which the PPA fails to provide an early priority date for later applications and patents. • Fourth, a summary of the major lessons in the book, organized by strategy, quality, and drafting of provisional applications. PROVISIONAL PATENT APPLICATIONS: Use and Abuse is intended to help patent professionals and inventors draft provisional applications clearly and broadly, thereby providing the early priority dates necessary to protect inventions. It is intended also for corporate and IP executives, as well as engineers, who are not actively involved in the drafting process but who want to understand how to make best use of the provisional format.