PURPOSE: Ulrasound-quided percutaneous renal biopsy in useful in diagnosis of renal diseases and assessment of progression. We performaed 420 cases of percutaneous renal biopsy in children since 1980. We analysis the method, results and complications. METHODS: We used modified Vim-Silverman needle or Biopty?gun (pat 4699154, BARD) with Toshiba, 4 MHz GCE-406, aspiration transducer. Sedation was done by demerol(1mg/kg IM) and chlorpromazine(0.6mg/kg IM) 30 minutes before doing biopsy. If needed, general anesthesia was done by ketamine(1mg/kg). RESULTS: Among 420 cases 410 (97.6%) were adequate for diagnosis. There were no life threatening complications such as bleeding or infections. None required blood transfusion or nephrectomy. Two cases developed minor perirenal hematoma, however subsided completely in 2 weeks. The histologic diagnoses in order of frequencies were as follow: MCNS 114(27.1%), IgA nephropathy 88(21.1%), H-S-P nephritis 58(13.8%), MesPGN 22(5.4%), AGN 22(5.4 %),FSGS 19(4.5%). CONCLUSIONS: We recommend renal biopsy with ultrasound localization in children, because it is very safe modality for biopsy.