OBJECTIVE: Sri Lanka's human, physical, social, and economic resources suffered a massive impact after the tsunami of December 26, 2004. To assist in preparing for future disasters, the authors sought to characterize the pattern of hospitalizations from the main impact zone in the Southern Province. DESIGN: Retrospective chart review. SETTING: Patients admitted to Teaching Hospital, Karapitiya, the only tertiary care hospital in the Southern Province. PATIENTS, PARTICIPANTS: All hospital admissions on the day of and week following the tsunami, and a random sample (5 percent) of admissions from the month preceding, and the 3 months following the tsunami were coded according to the International Classification of Diseases, 10th Edition, analyzed, and geomapped. INTERVENTION: N/A. MAIN OUTCOME MEASURE(S): The overall daily number of hospitalizations increased by 50 percent on the day of the tsunami and decreased in the following week. RESULTS: Before the tsunami, injuries typically accounted for 20 percent of hospital admissions. However, injuries were markedly higher (89 percent of the total) on the day of the tsunami and remained elevated (35 percent) during the following week. After the initial peak in injuries (including near drownings), there was no increase in the frequency of infectious, cardiac, or psychiatric admissions. CONCLUSIONS: Injuries (including near drownings) were the most common cause of admissions immediately after the tsunami. The distribution of specific diagnoses differed from that seen after other natural disasters such as earthquakes and hurricanes. A central aspect of disaster relief operations and planning includes a thorough understanding of the postdisaster health effects and changes in disease patterns.