Cystinuria is a hereditary disorder of cystine and dibasic amino acids (lysine, arginine, ornithine) transport across the luminal membrane of renal tubules and intestine, resulting in recurrent nephrolithiasis. Cystine stones frequently occur in the second or third decade of life with an occasional occurrence in infancy and in old age. Herein is presented the case of a 1-year-old girl with cystinuria and recurrent urolithiasis; the genetic basis of the disease was investigated by mutational analysis of the SLC3A1 gene. The data show that the present patient has an increased cystine (923.08 microg/mL) level and was heterozygote for M467T mutation.