BACKGROUND: Familial forms of steroid-resistant nephrotic syndrome with the histologic findings of focal-segmental glomerulosclerosis have frequently a genetic basis. For the non-familial forms this is still unresolved. PATIENTS AND METHODS: Ten children with non-familial steroid-resistant nephrotic syndrome along with focal-segmental glomerulosclerosis were tested for mutations in the WT-1 and NPHS2 genes. RESULTS: In 1 patient, a mutation in intron 9 of the WT-1 gene and in 1 patient a heterozygous NPHS2 mutation could be detected. Both abnormalities are important for the treatment modalities and prognosis. CONCLUSION: Additional studies will have to provide a solid basis for the recommendation of mutation analysis in non-familial steroid-resistant focal-segmental glomerulosclerosis.