Although the University of Leeds has attained something of a reputation for the quality of its scholarship in the history of science, few historians are aware of the impressive collection of early scientific and medical books and manuscripts to be found in the University libraries. In order to make the library resources more widely known, we embarked on a systematic survey of the contents of the main historical collections. We wanted not only to give a general impression of the particular strengths and distinctive features of each collection, but also to mention the interesting or rare copies of individual works to be found in them. We have, therefore, examined every book related to the history of science and medicine in the relevant collections, and in doing so we have uncovered a number of important items. For example, we have identified a book which was once in Newton's library, and a previously unrecorded copy of Joseph Black's chemical lectures. More generally, we had not suspected the true size and range of the Chaston Chapman Collection, which makes it a valuable resource for the history of alchemy and early chemistry; nor were we initially aware of the strength of the Historical Collection of the Medical and Dental Library. The wealth of the legacies to (and the discrimination shown in recent purchases for) the Brotherton and Special Collections also impressed us.