We have Studied how complex formation between calcium and ethylenediaminetetraacetate or citrate ions influences the surface texture and the size of passed oxalate-phosphate renal stones. The four hour concrement treatment by sodium citrate or ethylenediaminetetraacetate aqueous solutions strongly affects the stone texture and provides a mass loss of 6-15%. We have found a significant decrease of the calcium and phosphor content oil a concrement Surface and formation of appreciable cracks. Our results do indicate that the Ca-complexon interaction call be effectively applied for disrupting some types of renal stones and, especially, residual concrements, which frequently occurs after a surgical operation or an extracorporeal shock-wave lithotripsy. This Study provides ail additional quantitative physicochemical basis for this slightly invasive therapy.