Review of the sparse literature on the prognosis of asymptomatic and mildly symptomatic gallstones reveals a diversity of methods, definitions, and groups of patients studied, which makes it difficult to draw conclusions. It appears that serious symptoms and complications develop in about 1% to 2% of patients with asymptomatic gallstones annually, with fewer complications developing in later years than in years soon after gallstones are discovered. In patients with stones with mild symptoms, rates of the development of complications are perhaps a little higher, about 1% to 3% per year. In patients who are initially mildly symptomatic, cholecystectomy for severe symptoms probably is undertaken in 6% to 8% per year in the early years, decreasing with longer follow-up. Other than symptoms, no factors related to prognosis have been established. Acute cholecystitis is the most common severe complication of gallstones. Based on follow-up studies, obstructive jaundice, cholangitis, pancreatitis, and cancer of the gallbladder are infrequent complications. Risk of subsequent colon cancer should not ordinarily be a factor when cholecystectomy is considered. Analyses of cost-effectiveness have not demonstrated substantial differences in life expectancy between patients with asymptomatic gallstones who undergo immediate open cholecystectomy compared with watchful waiting.