Perflubron emulsion is a bromine-based particulate contrast agent that is taken up selectively by the liver and spleen after IV injection. It does not leave the vascular space and also persists in the blood for a longer period than iodinated contrast agents do. We performed a preliminary study to determine the value of the IV perflubron emulsion as a contrast material for CT and sonography. To determine the safety and dose response of perflubron emulsion as an IV contrast agent for CT and sonography, 18 cancer patients, 14 of whom had hepatic metastases, were given 0.5-3.0 ml/kg of the emulsion. Sonography and CT of the liver and spleen were performed before and immediately after infusion and then again at 24 hr. A persistent increase in the density of blood, liver, and spleen was observed, where maximal enhancements of 55, 39, and 317 H, respectively, were achieved. Tumor conspicuity increased as metastases enhanced minimally (7 H or less). Peak enhancement of the liver and spleen was delayed to 24 hr with higher doses of perflubron; however, the immediate postinfusion scan allowed the distinction of vessels from hepatic lesions. Sonographically, an increase in tumor echogenicity relative to liver was observed in nine of the 14 subjects, allowing the detection of additional metastases in two. Splenic echogenicity in the near field increased relative to kidney; however, attenuation increased markedly at the time of peak concentration, limiting beam penetration. Similar but milder changes were observed in the liver. Adverse effects occurred in 14 of the subjects; these included lower back pain in six, delayed fever in eight, and malaise in three. Perflubron emulsion produced prolonged enhancement of blood, liver, and spleen and increased the conspicuity of liver metastases. However, the side effects encountered could limit its use to a selected population of patients.