The management of asymptomatic cholelithiasis in patients with diabetes is controversial. We used decision analysis to compare expectant management to prophylactic cholecystectomy in asymptomatic diabetic patients. Relevant probabilities were derived from the literature or expert opinion. Hypothetical cohorts of patients were followed for their lifetimes under each strategy. Expectant management was almost always the superior course. For example, a 30-year-old diabetic man gains an average of 6.1 months of life by choosing expectant management over prophylactic surgery. The superiority of expectant management was invariant to changes in age, sex, and the extent to which major surgical complications affect the future quality of life. Prophylactic cholecystectomy was superior only with extremely high estimates of the likelihood of developing symptomatic disease, the probability of requiring emergency surgery after symptoms develop, and emergency surgical mortality rates. However, no single factor had sufficient impact to alter the optimal decision by itself; the probabilities of several untoward events had to be increased simultaneously to favor prophylactic cholecystectomy. Prophylactic surgery for silent gallstones in diabetic patients does not increase life expectancy or quality of life and may in fact reduce it. This result holds over a wide range of basic assumptions.