To measure testicular volume accurately, an ultrasonographic method was developed and the results obtained from this compared with those obtained by conventional measurements, namely (1) comparison with testis models, (2) an orchidometer, and (3) measurement of testicular volume by calipers through the scrotal skin. Data from these methods were compared with the actual volume measured at operation by slide calipers placed directly on the testis. The volume obtained by comparison with testis models or with an orchidometer tended to over-estimate the actual volume. The volume measured by slide calipers on scrotal skin was also found to be incorrect. On the other hand, the volume measured by ultrasonography proved to be closer to, and to correlate well with, the actual volume, and was considered to be the best method.