Oral magnetic particles in MR imaging of the abdomen and pelvis. Two phase 2 clinical trials of an oral superparamagnetic contrast agent for enhancement on magnetic resonance images of the intestine were performed. In trial 1, 31 male patients with cancer of the testis underwent follow-up examinations of the abdomen at 0.5 and 1.5 T after oral administration of magnetic particles. In trial 2, 31 female patients with pelvic and lower abdominal disease were examined at 1.5 T after administration of the contrast material. The patients each ingested 800 mL of contrast material over approximately 2 hours. Concentrations of 0.25 and 0.5 g/L did not induce blurring or metallic artifacts. Distribution was homogeneous through the gastrointestinal tract. In all patients, a loss of signal intensity was observed on proton density-, T1-, and T2-weighted images. The diagnostic information from postcontrast images in trial 2 was greater in 16 patients (52%). Contrast enhancement was independent of field strength; no major side effects were observed. Artifacts from moving bowels were less troublesome, and delineation of intraabdominal and pelvic organs was better with the use of oral magnetic particles. 