Information on the occurrence of renal stones was obtained in a health survey of 50-year-old men and at follow-up of the same group 10 years later. At the latter investigation, 338 of 1781 participants (19%) had a history of renal stone formation. In 47% there had been recurrences. For the individual there was a continuous risk of acquiring a first renal stone up to the age of 60. Approximately 0.5% of the entire unselected population experienced onset annually up to this age. Recurrent renal stones occurred primarily in those with a positive family history of stones or early onset of stones, as well as in those who previously had frequently formed stones. A carefully obtained clinical history should be useful in predicting recurrences in the individual stone former.