RESULTSThere were 30 renal units in 29 children (median age 3.8 years, range 1.4-5). Because of poor growth the mean ( SD ) body weight of the children was only 12.2 (2.8) kg, which is near the 50th percentile for children of mean age 3.5 years. The median (range) stone burden was 2.35 (1.3-6) cm; 60% of the patients had single stones while 28% had more than five. There were five staghorn stones. All PCNL was primary and with one puncture, using a 17 F angled nephroscope; stones were fragmented using a pneumatic lithoclast. After PCNL stones were completely cleared in 60% of the renal units, which increased to 100% after combining it with extracorporeal shockwave lithotripsy. The median (range) follow-up was 24.9 (4-51) months; the overall complication rate was 6%. In the long follow-up hypertension was not detected in any child and isotopic renograms in 17 kidneys detected no new scarring or loss of renal function. CONCLUSIONPCNL is a safe and effective for treating renal stones in very young children. KEYWORDS PCNL, renal stones, pre-school children OBJECTIVETo review our experience of percutaneous nephrolithotomy (PCNL) in children before school age, and determine its efficacy and safety in this age group. PATIENTS AND METHODSThe records of children aged £ 5 years undergoing PCNL were reviewed. Variables assessed included stone number, size, location and type. The PCNL puncture site and number were also recorded. We reviewed stone clearance with PCNL, ancillary procedures used, complication rates and follow-up status of the children.