This phase 1-2 trial investigated the use of a 100% wt/vol emulsion of perfluorooctylbromide (PFOB) in computed tomography (CT) of 30 patients with metastatic cancer. Injection of 3 g/kg (maximum dose administered to these patients) provided an average liver enhancement of +31 HU on CT scans obtained after 48 hours. Maximum splenic opacification occurred immediately after injection; 1 g/kg, which allowed an immediate enhancement of +35 HU, appeared sufficient for the diagnosis of splenic conditions. Vascular opacification was insufficient for diagnostic purposes. In four patients with metastases, more lesions were seen with the use of PFOB with CT than with conventional CT. Adverse effects included five cases of low back pain that were reversible when the infusion rate was reduced. Fever and trembling were also noted 6 hours after injection in five patients. In all patients, symptoms regressed spontaneously within several hours. Clinically inapparent and dose-independent splenomegaly (volume increase of at least 20% on CT examinations) was noted in eight patients.