A calculation model was developed for the cost of stone therapy and metaphylaxis in Germany based on estimates of stone incidence, types and recurrence rates, actual costs for stone removal and metaphylaxis (based on data from a district of the social health care system). There are 200,000 stone recurrences per year in Germany. Cost for treatment of these stones amount to $687,000,000. Stone metaphylaxis reduces the recurrence rate by some 40%. The annual cost for stone removal could be lowered by $275,300,000. Metabolic evaluation/metaphylaxis amount to $70,100,000 per year, resulting in an net saving of $205,200,000. In 1997, there were 96 days off-work per stone patient resulting in 5,800,000 days off-work in Germany per year. Metaphylaxis in stone formers can lower health care cost significantly. Although health care conditions may vary from country to country, in principle this calculation model is applicable also to other countries.