Background: Prion diseases are untreatable, progressive, and fatal brain disorders that occur worldwide, and the annual incidence rate is approximately 1 case per 1 million people. The duration of these diseases in Japan is unclear.<BR>Methods: Based on data from 1 April 1999 through 4 September 2008 provided by the Japanese Creutzfeldt-Jakob disease (CJD) surveillance program, we analyzed disease duration and its relationship with clinical features. Duration was assumed to be the time from disease onset to death.<BR>Results: Evaluation by the surveillance committee indicated that during the observed period 1128 individuals received a diagnosis of prion disease and were registered in the surveillance program. Mean disease duration in the 855 patients who died was 17.4 months. Overall, 46.0% of patients died within 1 year and 77.2% died in less than 2 years. Among those with sporadic Creutzfeldt-Jakob disease, which represented 77.0% of cases, mean disease duration was 15.7 months, while that of patients surveyed by the European Creutzfeldt Jakob Disease Surveillance Network (EUROCJD) was only 5 months.<BR>Conclusions: Disease duration among Japanese with prion diseases was much longer than that of patients in Western countries conducting surveillance of prion diseases. This finding suggests that the characteristics of the system for providing life-sustaining treatment for patients with fatal, progressive diseases in Japan are related to the longer duration of these illnesses.