In patients with rheumatoid arthritis, the presence of acute synovial inflammation is an indication of the activity of the disease. It is an important finding because it often influences therapeutic decisions. However, acute synovitis may be difficult to detect by clinical examination, especially if a joint effusion also is present. As gadolinium tetra-azacyclododecane tetraacetic acid (Gd-DOTA) can be expected to accumulate in areas of acute inflammation, we studied the value of Gd-DOTA-enhanced MR to determine the presence of acute synovitis. Nine patients with current knee symptoms underwent MR examination of the knee. Short and long TR/TE MR images were obtained with a 0.3-T magnet before and immediately after IV administration of Gd-DOTA. A 15-min delayed short TR/TE image also was obtained. Of eight patients with moderate to severe clinical evidence of acute synovitis, six had marked increase and two had moderate increase in signal intensity from synovial tissue on the short TR/TE image obtained immediately after administration of contrast material. In the ninth patient, who had minimal synovitis clinically, the signal from the synovium did not change after administration of contrast material. No difference was seen between the enhancement pattern on the immediate and the 15-min delayed images. These results suggest that Gd-DOTA is taken up by inflamed synovium and that Gd-DOTA-enhanced MR scans may be useful in detecting acute synovitis in patients with rheumatoid arthritis.