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To evaluate the risk factors related to the long-term outcome of endourologic treatment of urinary calculi, data from the rates of recurrence or re-growth in 145 patients with 167 renal units who were observed for more than 3 months at the Hiroshima University Hospital, were reviewed. The factors included in the present analysis were age, previous stone, location, number, size and composition of stone and procedures of treatment. Of 167 renal units, the overall recurrence and re-growth rates were 17% and 10%, respectively. The earliest recurrence and re-growth appeared at 3 months after the treatment, and 71%o of recurrence and 81% of re-growth occurred within 2 years. In 9 out of 20 renal units (45%) with unsuccessful treatment, residual stones enlarged during the follow-up. Stone located in renal calyx and pelvis, previous stone, multiple stones, size of stone more than 20 mm, stone composed of calcium oxalate and/or calcium phosphate and struvite stone were likely to be risk factors. However, on the univariate analysis there were no significance of difference among these variables. On the results of analysis by Cox's proportional hazards model, characteristics such as stone located in renal calyx and pelvis, size of stone more than 20 mm (p<0.01), treatment with percutaneous nephrolithotripsy (PNL), previous stone, size of stone between 10 mm and 20 mm, and multiple stones (p<0.05), were significantly related to either recurrence or re-growth of stone. Four variables, stone located in renal calyx and pelvis, previous stone, upper ureteral and UPJ stone, and size of stone between 10 mm and 20 mm, were entered by stepwise selection, resulting that the last one was an inhibitory factor and the others were promoting factors. Logistic regression analysis also showed that previous stone, unsuccessful treatment, stone located in renal calyx and pelvis, and multiple stones were significantly related to either recurrence or re-growth (p<0.05). Results obtained by the stepwise selection demonstrated that 3 variables, previous stone, treatment with PNL and unsuccessful treatment, were promoting factors and one variable, age more than 61-year-old, was an inhibitory factor. On the prediction of recurrence or re-growth using above 4 variables, the correct diagnosis was 67.0%. Both analyses by Cox's proportional hazards model and logistic regression analysis indicated that chalacteristics such as previous stone, stone located in renal calyx and pelvis, and multiple stones were significantly correlated with recurrence or re-growth of stone. In these variables, previous stone was the most important risk factor. These results indicate that periodical checkup including a preventive procedures is mandatory in a high risk patient.