Two-hundred ninety-eight patients with gallstones accompanied by mild or nonspecific symptoms, 123 with asymptomatic gallstones, and 46 with nonfunction on cholecystogram and mild or nonspecific symptoms were followed in the setting of a health maintenance organization for up to 25 years after diagnosis. In a life-table analysis, complications (severe events) developed in about 1% per year of patients with visualized gallstones and in about 2% per year of patients with nonfunction. During each of the first 5 years after diagnosis, all events, both severe and non-severe (including surgery for continuing mild symptoms) occurred in about 6% of the patients with mild symptoms accompanying either gallstones or nonfunction, and in about 4% of patients with asymptomatic gallstones. The annual probabilities for all events tended to decrease as length of follow-up increased. Among patients with stones and mild symptoms, women were more apt to develop any event than men (p = 0.02) and more obese patients were more likely to develop severe events than those who were thinner (p = 0.05). The patients in this study are probably more representative of outpatients with gallstones seen by most primary care physicians than are most groups investigated previously for prognosis. Their event rates are sufficiently similar to those used in published decision analyses, that they should not alter previous conclusions that early elective cholecystectomy will have little positive or negative effect on average life expectancy of patients with gallstones.