Cystone will be used in proven cystine and calcium stone forming adults who are not pregnant. Subjects must have a measurable stone by CT. The first phase is a double blind, randomized, placebo controlled cross-over of Cystone and placebo for 6 weeks each separated by a 1 week washout. Entry, 6 and 12 week 24 hour urine supersaturations or cystine, pH and sodium determinations will be collected. Then all patients enter an open label phase of 46 weeks, ensuring a 52-week total exposure to Cystone during the 59 week study. Baseline and 1 year stone quantification CT scans will be performed. End points will be changes in urine chemistry/supersaturation and stone burden. Stone burden was measured by CT, quantitatively for stone density and volume. All CT images were also reviewed in a blinded fashion by a radiologist to score each kidney as increased, no change or decreased stone burden.