The role of psychosocial factors in peptic ulcer remains controversial. We have investigated the relationship between socioeconomic status, concrete stressors, and ulcers in a longitudinally followed, population-based cohort, taking confounding risk factors into account. A total of 6,928 adults completed the Alameda County Study's baseline questionnaire in 1965; 4,595 ulcer-free on enrollment responded again in 1973-1974. Reported cases of ¿stomach or duodenal¿ ulcer during the year before each of the two surveys were examined with relation to 1965 characteristics: 288 subjects reported ulcers at baseline, and 104 reported new ulcers on follow-up. Sociodemographic characteristics associated with incident ulcers (age-adjusted) were, in women, low education, a blue-collar household, overcrowding, unemployment, marital strain, and children's problems; in men, nonwhite race. Prevalent ulcers were associated in women with sociability and children's problems; in men, with blue-collar occupation, low education, financial difficulties, marital strain, children's problems, and a sense of failure. Adjustment for smoking, alcohol, chronic bronchitis, arthritis, liver disease, and skipping breakfast weakened but did not eliminate these associations; adjustment for socioeconomic status further attenuated the associations of specific problems. Low socioeconomic status and concrete life difficulties are associated with peptic ulcer in the general population cross-sectionally and prospectively after adjustment for major physical risk factors, lending credence to a relationship between psychological stress and peptic ulcer.