The pharmacokinetics of oral and intravenous bromide was studied in 7 adult volunteers, who served as their own controls. They received 1 ml/kg of 3% sodium bromide, equivalent to 30 mg/kg bromide. Oral bioavailability ranged between 75-118% with a mean of 96 +/- 6%. Elimination T1/2 was 11.9 +/- 1.4 days after oral administration and 9.4 +/- 1.5 days after I.V. administration (P greater than 0.10). The employment of this ion for calculation of extracellular fluid and assessment of its potential significance in environmental toxicology necessitates accurate data on its disposition characteristics.