For nearly three years we have been using implants of polymaleinate ionomer in the reconstruction of the ossicle chain (Figure 1). Implants of this material can be easily formed by a diamond drill. An implant in site 18 months later is to be seen in Figure 2. From August 1990 through April 1993 this material has been implanted into 156 middle ears. Only one implant had to be explanted again for a second-look operation in cholesteatoma. Extrusion or any tissue reaction on the foreign substance could not be seen. The implant was examined histologically. It was covered by mucosa and not destructed anyway (Figure 3). According to the extension of a cholesteatoma we take away the dorsal wall of the ear canal for reasons of sanitation and leave a radical mastoid cavity in children. In adult patients we tend to reconstruct the ear-canal to avoid the disadvantages of a radical mastoid cavity: Frequent treatments and hearing-loss by resonance-shifting (2). For reconstructing the dorsal wall of the ear-canal cartilage of the concha and tragus is well qualified. In support of experimental and clinical experience of the Würzburg group (1) we take ionomer micro-implants for reducing large radical mastoid cavities (Figure 4). The radical mastoid cavity is finished by the diamond-drill before being filled up with micro-implant in the dorsal parts. The micro-implant is covered by a flap of periost and connecting tissue. Figure 5 shows a situation operated by this technique 20 months ago, Figure 6 shows the result after operation of a former secerning radical mastoid cavity.(ABSTRACT TRUNCATED AT 250 WORDS)