Objective. The purpose of this study was to investigate whether an inguinal hernia would have an impact on the testicular volume and blood flow by scrotal ultrasonography. Methods. Twenty-six male patients with unilateral inguinal hernias with a mean age of 48.1 years were included in the study. Testicular volumes were calculated, and spectral parameters such as the pulsatility index and resistive index of the testicular artery at supratesticular, subcapsular, and intratesticular levels on both the side with the inguinal hernia and the contralateral side were measured by a preoperative ultrasonographic examination. Comparisons between the dependent groups were performed by a Wilcoxon or paired samples t test where appropriate. Results. The mean +/- SD testicular volume on the side with the inguinal hernia was significantly higher than that on the contralateral testis (15.46 +/- 4.49 versus 14.54 +/- 3.65 mL, respectively; P <.05, Student t test). In addition, the mean resistive index of the intratesticular arteries was significantly higher on the side with the hernia compared with the contralateral side (0.66 +/- 0.06 versus 0.63 +/- 0.05; P <.05, Student t test). Conclusions, These data indicate that an inguinal hernia may impair testicular blood flow, which may be attributable to an intermittent mechanical compression effect on the funiculus spermaticus in the inguinal canal.