Incidence and risk factors for peptic ulcer disease in the United States have not been well defined, During the 1989 National Health Interview Survey, a population-based sample of 42,392 individuals responded to questions regarding doctor-diagnosed ulcers with confirmation by either an upper gastrointestinal series or endoscopy, Ulcers present during the previous 12 months were considered either incident ulcers if diagnosed during this period or chronic active ulcers if diagnosed more than 12 months before the interview. The incidence of ulcers over the year prior to the interview was 5.27 per 1,000 adults, Whereas incident duodenal ulcer cases represented only 2.4 percent of all persons with a history of duodenal ulcer, the corresponding value for gastric ulcer was 8.7 percent, Risk factors for incident ulcers included increasing age, lower income and educational attainment, and musculoskeletal pain or headache, These were similar to risk factors for chronic active ulcers, except smoking was an additional important risk factor for chronic active ulcers. Thus, incident peptic ulcers are common in the United States but represent a small proportion of persons with a history of ulcer disease. Smoking may be a stronger risk factor for chronic ulcers than for new ulcers.