Routine screening by mammography and physical examination can detect breast cancers earlier at all ages. In women over age 65 the sensitivity of mammography is increased, and the positive predictive value for mammography is higher than in younger women. There are no direct data that can be used to determine at what age screening is no longer of value. This question must be evaluated on an individual basis and should take into account the quality of life and competing causes of death. The medical benefit from screening for a given individual should be considered separately from society's cost/benefit goal to reduce health care expenditures, because the two are likely to produce contradictory recommendations.