Patients older than 80 years of age are the most rapidly increasing group among surgical admissions and patients visiting emergency rooms. Epidemiological data of this group are of enormous medical and economic relevance. The principle aim of this study was to determine factors predictive of operative mortality in octagenarians, their clinical profiles, and length of stay compared to younger patients in similar diagnostic categories. A computer-based registry of geriatric surgery was used to record and analyze all relevant clinical and epidemiological data. The rate of admissions in octogenarians increased during the 18-year period (1973-1989) from 0.7% to 7.5% of all admissions. The number of patients undergoing surgery was 700. Three hundred and seventy-one of the procedures were elective and 329 were emergencies. Operations in octagenarians as a percentage of all operative procedures increased during the period considered from 1.1% to 5.1%. The operative mortality in this series was 10.5% prior to 1984 and decreased to 6% during the last 5 years. The average hospital stay of octagenarians was 9.8 days as opposed to 4.9 days in patients less than 70 years of age. The prognostic classification described by the authors proved very helpful in predicting mortality.