Vascularization of the testis through testicular artery is of great importance to maintain its normal function. Vascular disruption due to inadequate arterial blood flow of the testis negatively affects testicular function and semen quality. This study aimed to determine the efficacy of gonadotropin-releasing hormone (GnRH) administration on testicular vascularity in relation to testosterone hormonal response. Five clinically healthy adult ossimi rams 18- to 30-months-old were used. Testicular arteries Doppler examination, blood sampling following GnRH administration and testosterone hormonal assay were conducted. Both pulsatility index (PI) and resistance index (RI) significantly decreased in all treated rams starting from 1 hr till 120 hrs after single GnRH administration, both Doppler indices returned to their pre-treatment values at 144 hours after GnRH administration. Doppler peak systolic velocity (PSV) did not change in response to GnRH administration. Testosterone hormone concentrations negatively correlated with PI and RI but not PSV. In conclusion, GnRH would be useful a beneficial therapy for treatment of testicular dysfunction in rams by increasing testosterone concentrations and testicular blood flow. And pulse wave Doppler ultrasonography would be a useful non-invasive clinical tool for evaluation of the efficacy of novel therapeutic treatments in rams.