The lamina propria of the human tympanic membrane consists mainly of collagen fibres, but vessels and nerves can also be found as solitary elastic fibres. The pathologic alterations of the collagen fibres were examined by 47 biopsies of the tympanic membrane. These biopsies were taken in various middle ear diseases, and pathological changes were found in every case, ranging from clotting to chondral metaplasia; in one case a metaplasia into osseous tissue was found. No relationship was seen between the otoscopic findings and the severity of the pathological changes.