The story of the relationship between diagnosis at the bedside and the bench has been filled with tensions by historians of medicine. However, unpublished sources such as hospital case notes, minute books and private notebooks provide evidence that elite physicians were enthusiastic about new diagnostic techniques. With case studies of St Bartholomew's Hospital, London, and Addenbrooke's Hospital, Cambridge, this paper explores debates around the establishment and financing of the laboratories and their staff, along with patterns of diagnostic practice. In particular, the use of bacteriology by Barts' physician, Samuel Gee, is compared to his public and private writing on laboratory science. The laboratory and pathologists were quickly and routinely used at Barts by elite physicians, even more so than at Addenbrooke's, which had links with the University of Cambridge, a university famous for laboratory research at this time.