To elucidate whether SLC1A5 is involved in the aetiology of cystinuria, we screened two non-type I cystinuria families without detectable mutations inSLC7A9 (and SLC3A1) but compatible with linkage to 19q13 for genomic variants in SLC1A5. Despite evidence for an involvement of SLC1A5 in the aetiology of cystinuria, we could not identify any mutation in this gene in the two families. With SLC1A5, a further candidate gene for cystinuria can be excluded as being involved in the pathogenesis of this disease in these two families. Of course, there remains the possibility that other genes are involved in cystinuria; further molecular studies will clarify the complex nature of this disorder.