UROLITHIASIS or urinary tract stone disease is a major health problem in the United States. Using discharge diagnoses of hospitalized patients, Boyce et al1estimated the incidence of urolithiasis at 7.9 patients per 10,000 population while Sierakowski et al2reported that 16.4 patients per 10,000 were at risk for the development of urinary tract stone disease. It is estimated that 2% to 5% of the general population will experience renal colic at some time during their lifetimes, with a 20% to 50% risk of stone recurrence.3The economic implications of urolithiasis also are significant. In 1987, medical costs directly attributable to inpatient management of stone disease exceeded $ 1 billion.4Because many patients with urinary tract stone disease are managed on an outpatient basis, the true incidence and economic impact of urolithiasis are probably underestimated.