This article presents the results of a preliminary investigation into the risk of very large earthquakes in Sumatra. Data for the study were taken from the Earthquake Data Base System of the National Earthquake Information Center, U.S. Geological Survey. In determining the recurrence interval of large earthquakes, the method of Dong et al. (1984) based on the maximum entropy principle was used. If the maximum magnitude of possible earthquakes in Sumatra is assumed to be 8.75, 9.0, or unlimited, the recurrence interval of a magnitude 8.5 earthquake is found to be 430, 283, or 204 yr, respectively. For the three cases, the magnitude of an earthquake with a 10% probability of exceedance in 50 yr is determined to be 8.52, 8.64, and 8.85, respectively, on the assumption of Poisson's distribution for earthquake occurrence. The results imply that the risk of a very large earthquake is high in Sumatra, and its consequences on the distant metropolitan areas on the Malay Peninsula should be investigated in further research.