The strength and unity of the medical library profession spring largely from the existence of the National Library of Medicine. Its publications promise to bring much closer the standardization and consistency still lacking to the world of medical subject headings. The Wellcome Library headings are similar to those listed in the National Library of Medicine Subject Heading Authority List of 1960. However, references and additional headings are made to cover (1) superseded terms, (2) historical phenomena with distinctive names which are peculiar to an epoch, (3) subjects from social, religious, or other branches of history, and (4) eponyms. Old texts often describe disease ambiguously or use terminology which has since been superseded. The catalogue is in three parts-topographical, biographical, and topical. The quarterly Current Work has certain simplifications (e.g., elimination of some subheadings), and has recently introduced references both to cut down needless duplication and to facilitate consultation by the reader.