Background: Consumption of nonaspirin nonsteroidal anti-inflammatory drugs (NANSAIDS) increased substantially during the 1980s. The effects of this trend on hospitalization rates for peptic ulcer in different age groups in New South Wales, Australia, was investigated. Methods: A population model based on sales of NANSAIDS and aspirin, age specific estimates of the relative risk of ulcer complications with these drugs, and hospitalization data for 1979 through 1988 was created. Results: All age groups increased consumption of NANSAIDS. The increases were greatest in elderly subjects, with women over age 65 years increasing the prevalence of their use of the drugs from 11.9% in 1979 to 22.5% in 1988 and males over age 65 increasing use from 9.7% to 20%. Aspirin use remained relatively unchanged in all age groups. Hospitalization rates for peptic ulcer decreased in both sexes under age 64 despite increasing use of NANSAIDs. Hospitalization increased in males and females over age 65, but in females the increase was substantially greater than predicted by the computer model. In women and men over age 75 the increases in hospitalization rates predicted by the model were only 18% and 33%, respectively, of the observed rises. Conclusions: The increasing hospitalization rate for peptic ulcer among elderly subjects was only partly explained by the increasing consumption of NANSAIDS. Further research is needed.