Perfluoroctylbromide (PFOB) has been applied successfully as an oxygen carrier and a contrast agent for X-ray, computed tomography, ultrasound and Magnetic Resonance Imaging (MRI). Knowledge of the pharmacokinetics of emulsion particle uptake and elimination is critical for determining proper dose and timing of diagnostic studies. This study was intended to define major organ biodistribution and half-life as well as total body half-life as a function of dose. Determination of biodistribution and major organ half-life was achieved by administering 100% PFOB emulsion intravenously to 180 rats divided into 3 dose groups of 0.3, 0.6 & 1.0 g/kg. Each group was divided into 6 subgroups (n = 10; S male and 5 female). Each subgroup was sacrificed at either 6 or 90 min., 1,2,7, or 28 days post injection. 16 different tissue samples were collected and PFOB concentration determined by iso-octane extraction and gas chromatographic (GC) analysis. Total body half-life was determined by administering PFOB intravenously to 60 rats divided into 3 dose groups of 0.6, 1.5 & 5.0 g/kg. Each group contained 10 pairs (5 male and S female). Pairs were placed in a metabolic cage at 1, 6 & 12 hrs., 1, 2, 4, 7, 11, 16, & 21 days following PFOB infusion. The metabolic cage facilitated the seperate collection of expired air, urine & feces. PFOB was extracted from expired air by a series of iso-octane traps. PFOB losses from expired air, urine and feces were quantified by GC analysis.