Cochlear implants are an accepted means for the treatment of profound bilateral deafness. Magnetic resonance imaging (MRI) is gaining more and more importance as a diagnostic tool. It is therefore very likely that cochlear implant wearers will, at some point in their life, become MRI candidates. This makes a discussion of MRI safety of cochlear implants a most timely subject. With the C40/C40+ system as an example, all the major and potentially troublesome interactions are discussed, as well as the conditions for the safe conduct of MR examinations with cochlear implant wearers. For the C40/C40+ systems, safe MR imaging is possible with 0.2 Tesla, 1.0 Tesla and 1.5 Tesla scanners. Copyright © 2001 Whurr Publishers Ltd.