Objective. To reveal the disease activity in Crohn disease by gray scale and Doppler ultrasonography of the superior mesenteric artery (SMA) and the affected bowel segments. Methods. Twenty-six patients (12 with active and 14 with inactive disease according to the Crohn disease activity index) were prospectively evaluated with gray scale and Doppler ultrasonography. The control group included 10 healthy subjects. In the SMA evaluation, anteroposterior diameter, resistive index (RI), and flow volume were measured. In the affected small-bowel segments, wall thickness, mural vascularity, RI, and extraintestinal findings were evaluated. Results. Differences between the active and inactive groups but not between the inactive and control groups were statistically significant for mean SMA diameter, RI, and flow volume (P = .019; P < .001; and P < .001, respectively). Superior mesenteric artery flow volume values were higher than 500 mL/min in the active group except 2 patients (sensitivity, 83%; specificity, 100%). Increased gut wall thickness and vascularity were highly significant for patients with active disease (P < .001). The mean SMA RI value of the active group was significantly lower (P < .001). Doppler measures of vascularity were similarly affected in the SMA and the bowel wall in the active subgroup. In 10 patients with active disease and higher SMA flow volume (>500 mL/min), the affected small-bowel segments also had increased wall thickness and vascularity. Conclusion. Evaluation of the SMA and the affected small-bowel segments together by gray scale and Doppler ultrasonography is a reliable quantitative method for determining Crohn disease activity. Findings obtained from both the SMA and the affected small-bowel segments showed parallel results about the disease activity.