The authors describe the surgical technique and results of the Nucleus device in 50 recipients. Cochlear ossification was present in one third of patients. Total insertion was possible in all cases with a partial ossification (< or = 8 mm), and once in a case with a total ossification (> 8 mm) of the scala tympani of the basal turn. Results were not significatively different in normal cochleas and in ossified cochleas. The authors describe a per-operative algorithm in front of a basal turn ossification, emphasizing on the insertion in scala vestibuli through the oval window. According to the results, the authors prefer the use of a multi-channel cochlear implant than a monochannel implant, even in ossified cochleas.