Technical Abstract: espiratory clearance of selenium may be important in the toxicity of inorganic and organic selenium. The purpose of this study was to investigate the elimination of organic and inorganic selenium through respiration, following acute oral dosing in lambs. Thirty eight crossbred lambs, 8 - 12 wk of age, were randomly divided into 8 groups of 4 lambs and orally administered a single dose of 0, 1, 2, 3, or 4 mg/kg BW as sodium selenite (inorganic selenium, NaSe) or selenomethionine (organic selenium, SeMet. Expired air was collected from all animals at 4, 8, and 16 h post-dosing. SeMet treatments had a greater respiratory Se elimination when compared to their NaSe equivalents. Animals belonging to the higher dosage groups exhaled a larger amount of Se, and for a longer period of time. No correlation was seen between the time of peak selenium concentration in whole blood or serum and the peak concentration in the exhaled air.