Objective To investigate the condition of infants with urolithiasis caused by melaminetainted powdered formula at one-year follow-up. Methods Eighty-one young children with melamine-induced urolithiasis were followed up,which included urinalysis,renal-function tests,urinary tests for biochemical markers of renal glomerular and tubular function,and ultrasonography.Eighty-one age-matched healthy infants without exposure to melamine-contaminated formulas were enrolled as controls. Results Fifty-one of the patients were male and 30 female,with a mean age of 26 months (range 13 -48 months).The 81 children were divided into 2 groups according to treatment protocols.Group 1 received conservative treatment ( n =54 ) and Group 2 received surgical treatment ( n =27 ).In Group 1,3 patients (5.6％) had stone-residual:1 girl had calculus of 0.4 cm in diameter in the left kidney and 2 girls had calculus of 0.3 cm in diameter in the right kidney.In Group 2,2 patients (7.4％) had stone-residual,1 boy had crystallization of 0.2 cm in diameter in the right kidney and 1 boy had calculus of 1.5 cm in diameter in the left kidney,positive stone was confirmed by X-ray and accepted percutaneous nephrolithotomy.Urinary microalbumin levels were significantly increased in the children with melamine-induced urolithiasis compared with the control group (P ＜0.01 ).Blood urea nitrogen and serum creatinine were within the normal range with no significant difference between the 2 groups. Conclusions At one-year follow-up most of the children exposed to melamine-tainted infant formula in both treatment groups had returned to a healthy state,suggesting a satisfactory outcome for both treatment options.However,surgery is recommended in patients with stoneresidual ＞ 10 mm.