The number of Americans at least 100 years old is expected to grow dramatically over the coming years. In December 2010, 71 991 centenarians lived in the United States, almost double the number there were 20 years ago.1, 2 By 2050, the number of centenarians is expected to reach 601 000, a 735% increase.2 Despite the growing numbers, the health care use of this population remains largely unexamined. In particular, the rates and outcomes of hospitalization for persons 100 years or older are unknown. The goal of this study was to determine rates of hospital admission as well as in-hospital all-cause and diagnosis-specific mortality in patients 100 years or older.