OBJECTIVE: To assess the value of ultrasonography in the preoperative localization of undescended testes in children. PATIENTS AND METHODS: A prospective study of 32 boys who presented with 44 undescended testes at the Paediatric Surgery clinic in LUTH from July 2010 to June 2011. They were all examined at the clinic and subsequently had ultrasound assessment at the Radiology department before they were operated upon. The demographic data, predisposing factors, preoperative location of the testes by physical examination and ultrasound and findings at surgery were recorded. The accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of ultrasound were determined and compared with that of physical examination and intra-operative findings. RESULTS: There were 44 undescended testes in the 32 boys. 12 were bilateral, 12 were on the right and 8 on the left. On physical examination, 17 testes were palpable while 27 were non-palpable. Ultrasound localized 38 testes preoperatively. Forty-one (93.2%) of the 44 testes were located at surgery. Three (6.8%) were absent and thought to be vanishing testes Ultrasound correctly localized 36 (87.8%) out of the 41 testes found at surgery while physical examination correctly localized 17 (41.4%) . Ultrasound was more accurate than physical examination (p= 0.000) and had comparable accuracy with intraoperative localization (p=0.109).Ultrasound evaluation had a sensitivity of 87.8%, specificity 33.3%, PPV 94.7%, NPV 16.7% in preoperative localization of undescended testes. CONCLUSION: This study shows that ultrasonography is of value in improving the accuracy of preoperative localization of undescended testes in children.