Cochlear implantation is regarded as a safe and effective treatment for the profoundly deaf. However, a proportion of patients suffer complications after implant surgery. This paper examines the complications encountered in 240 adult cochlear implant operations performed in Manchester between June 1988 and June 2002. Minor complications were defined as those that either settled spontaneously or with conservative management. The total number of minor complications was 61 (25.4 per cent of cases). Non-auditory stimulation, which resolved with implant reprogramming, was present in 53 cases (22.1 per cent). Major complications were defined as those requiring further surgery, explantation or causing a significant medical problem, and occurred in 15 patients (6.25 per cent). These included implant extrusion, implant sepsis, electrode migration, flap-related problems, and persistent non-auditory stimulation. Nine of the 15 patients suffering a major complication required explantation. There were no post-operative deaths, cases of meningitis, nor persistent facial palsies in the series.