Urinary calculi were found in 4,500 hospital patients during a period of thirty-five years. Studies were made on 2,693 such stones either recovered clinically or removed at autopsy. The stones were found oftener in men than in women and oftener in the ureter than in the kidney. They were analyzed by petrographic crystallography. Calcium oxalate was the major mineral component of most of the stones encountered. Oxalate stones occurred more frequently in men and phosphate stones more frequently in women. About 20% of the oxalate stones were readily identifiable as primary, in the sense of having formed on a renal papilla, for they bore a definite indentation as if molded over a papilla and had a rough depression marking the point of attachment. The rate of 25 urinary stones per 1,000 patients discharged from this hospital was more than three times the estimated national average but is believed to be representative of the southeastern part of the country, which includes North Carolina.