This is a new edition, revised and expanded, of a seminal work in the logic and philosophy of time, originally published in 1968. Arthur N. Prior (1914-1969) was the founding father of temporal logic. His work has attracted increased attention in the decades since his death: its influence stretches beyond philosophy and logic to computer science and formal linguistics. Prior's fundamental ideas about the logic of time are presented here along with his investigations into the formal properties of time and tense. Already in 1969 Prior had been planning a new edition of Papers on Time and Tense, to incorporate his more recent work. Because of his untimely death this plan was never followed through--till now. Seven important papers have been added to the original selection, as well as a comprehensive bibliography of his work and an illuminating interview with his widow, Mary Prior, about his life and work. In addition, the Polish logic which made the original book difficult for many readers has been replaced by standard logical notation. This new edition will secure the classic status of the book.