OBJECTIVE The purpose of this study was to determine the normal range of renal length in Hong Kong Chinese children and compare it with Western data. METHODS Two hundred fifty children undergoing routine abdominal sonography were examined prospectively, and the maximum length of 1 kidney per child was recorded. Ages ranged from newborn to 19 years, and there were 109 girls and 141 boys. Similar data from Australian children involved maximum lengths of both kidneys in 554 children ranging in age from newborn to 14 years. There were 361 girls and 193 boys. No children had known renal disease. RESULTS There was no statistically significant difference between the mean renal lengths of girls and boys. Statistical comparison of the data from Hong Kong and Australia showed no significant difference except in the 8-12 month age group (this difference is unlikely to be clinically significant). Although direct statistical comparison with published data on kidney lengths in 203 U.S. children was not possible, plots of the three sets of data were strikingly congruent. CONCLUSIONS Despite expectations that smaller body size in Hong Kong children might equate to smaller kidneys, comparison with 2 sets of Western data showed no clinically significant difference in renal length between the 3 groups.