PURPOSE: To evaluate the useful criteria of resistive index (RI) in diagnosis of the acute scrotal inflammation using Doppler ultrasonography. MATERIALS AND METHODS: Twenty-two patients with acute scrotal inflammation wen. included in this study frorn Nov. 1994 to Nov. 1997. Mean resistive indeces were obtained by means of Doppler ultrasonography. Statistical difference between diseased and control side was assessed and cutoff value of RI was established for diagnostic criteria. RESULTS: Color Doppler flow was increased in diseased testis and epididymis in all 22 patients. Mean RI of diseased sides was 0.54 and that of normal sides was 0.75, and RI between normal and diseased sides was statistically different (P=0.0001). Setting 0.60 as the cutoff value, specificity was 100%, accuracy 95 %, sensitivity 91 %. CONCLUSION: Resistive index obtained from pulsed Doppler ultrasound and findings of color Doppler ultrasound were useful in evaluation of acute scrotal inflammation.