A high calcium intake reduces the severity of osteoporosis. Although dairy products are rich and inexpensive sources of calcium, these products contain large quantities of lactase, a sugar that is digested with difficulty by an appreciable fraction of the population. The resultant malabsorption of lactose may produce abdominal symptoms, a condition known as lactose intolerance. To prevent these symptoms, many individuals mistakenly believe they must either avoid all dairy products or use commercial digestive aids. This article reviews the role of calcium and dairy products in osteoporosis with particular emphasis on the importance of lactose intolerance as o deterrent to ingestion of dairy products. We conclude that problems resulting from lactose intolerance have been overemphasized, and virtually all subjects can ingest at least 1 cup of milk per day with breakfast without recognizable symptoms. Thus, lactose digestive aids should be reserved for higher doses of milk. Alternatively, lactose intolerant subjects who wish to ingest large quantities of dairy products can eat yogurt (which contains bacterial lactase) or hard cheeses (which contain minimal amounts of lactose).