Dr. DONALD BENTLEY, late senior houseofficer, the London Hospital, London E.1, and Mr. JOHN CLINE, medical technologist/engineer, write: A vast quantity of literature has been produced on the subject of finger-clubbing. Much has been written about possible aetiological factors and conditions in which clubbing is seen. Relatively little, however, has been. reported on what is undoubtedly one of the most important aspects of this topic namely, a rapid, simple to operate yet inexpensive technique of clubbing measurement-and few have attempted to equate it precisely. We decided to create a machine which by reflection would produce a magnified image of the finger on a screen. Detailed examination of the shadow could then be made. The present device is a cylindrical unit, the casing of which is made of nylon, with an oblique hood projecting beyond the screen (Fig. 1). The visor and casing are built on two metal rings. A square tin containing a 4.5-volt battery forms a platform and also acts as ballast. On the top of the device is a