Cystinuria is an inherited disease characterized by the formation of cystine calculi in the kidneys, ureters, and bladder. Cystinuria is associated with mutation in the SLC3A1 and SLC7A9 genes. These defects prevent appropriate reabsorption of dibasic amino acids lysine, ornithine, and arginine. Cystinuria is classified as type I (silent heterozygotes) and non-type I (heterozygotes with urinary hyperexcretion of cystine). In molecular term, cystinuria is classified as type A (mutations on SLC3A1 gene) and type B (mutations on SLC7A9 gene). This report describes 7 patients with early onset of cystine calculus formation. We are report a new mutation in SLC3A1 gene in exon 1. A novel nucleotide substitution c.-29A>G was found in exon 1 of the SLC3A1 gene, which had not been reported elsewhere previously.