The overall aim of Phase I and Phase II is to determine, if any, of the established urinary chemical abnormalities central to the pathogenesis of nephrolithiasis can be used prospectively to predict new onset of kidney stone disease in non-stone forming family members of calcium stone formers. This study proposes to measure potential urinary risk factors in all first degree relatives of the stone former (proband) upon entrance into the study and then follow subject for an average of 5 years in order to record stone formation and related morbidity. We will use a multivariate discriminate analysis to determine the independent predictors of new onset stone formation in family members. Family members at high risk might benefit from subsequent changes in lifestyle, diet, fluid intake or, possibly, pharmaceutical intervention that could stave off stone disease. To date no clinical trials have examined whether metabolic (laboratory) evaluation of health family members can predict stone formation. In addition to the established urine chemistries, we will examine whether a crystal growth assay can be a useful tool in predicting new stone formation. PROPOSED COMMERCIAL APPLICATIONS: Because of the extreme pain and suffering faced by kidney stone formers, many family members of stone formers are concerned about the possibility of their developing the disease. If we are able to establish which urinary markers for stone formation are predictive of disease onset in family members of stone formers, we will have developed a new indication for the testing which we currently sell.