Testicular size measurement is an important parameter in the assessment of testicular function in children, adolescence and adult since it correlates well with the mass of seminiferous tubules present. Measurement of testicular volume could be used to evaluate the normality of puberty, and can also be used to assess the effects of disease or treatment on testicular function. Various methods have been developed for the measurement of testicular volume. However, not all of them have been shown to be accurate especially in the measurement of testicular volume in children. This prospective study, therefore, was performed to determine the correlation between testicular volume measured with the Prader orchidometer, high resolution ultrasonography and intra-operative measurements using calipers in children. Also the study assessed the effect of age on the measured testicular volume. The study was carried out over a period of 17 months from January 2007 to May 2008. During this period, a total of 90 boys presenting for surgery for non emergency inguino-scrotal conditions were recruited into the study. The boys were examined in the clinic, and a Prader orchidometer was used to measure both the right and left testicular volumes. The examiner warmed his hands by rubbing them together for about seconds and the scrotal skin was stretched tightly over the testis to obtain such measurements. The patient was sent to a radiologist who measured the testicular volumes using a high resolution ultrasound machine (US). The radiologist was unaware of the orchidometer estimates. At surgery, the surgeon delivered the testis of only the pathologic side into the wound, and measured the testicular dimensions with a vernier caliper after opening the tunica vaginalis. The testicular volumes by US and caliper were calculated using the formular 0.71 x length x width x height. Statistical analysis of the results were performed to determine the correlation of orchidometer measurement with US measurements, the correlation of orchidometer measurements with caliper measurements and the correlation of US measurements with caliper measurements. The level of significance was set at P< 0.05. The ages of the boys ranged from 18days to 13years (median 3 years). There was a significant correlation between testicular volumes measured with the orchidometer and US (r= 0.540 – 0.566; P< 0.001), significant correlation between testicular volumes measured with the orchidometer and caliper (r= 0.678 –0.784; P< 0.001), and there was also a significant correlation between volumes measured by US and those measured by caliper (r= 0.414 – 0.851; P< 0.01). The testicular volumes did not seem to change consistently with chronological age. From the findings, the Prader orchidometer testicular volume estimates correlated significantly with US estimates in children. It is thus recommended that in resource strapped settings, an experienced examiner can use the Prader orchidometer which is relatively cheap, for an accurate and quick testicular volume assessment