1. Experimental fat embolism was produced in rats by intravenous injection of Triolein tagged with I131.
2. A qualitative and quantitative analysis was made of the distribution and concentration of radioactivity in various organs and tissues in relation to time.
3. The lungs proved to be efficient filters for the fat emboli. No other organs collected or concentrated more than 1 per cent of the total amount injected.
4. The fat accumulated in the lungs did not flow out, but was metabolized. The slowly increasing concentration of free iodine in the thyroid in these rats was indicative of this process.
5. The absence of evidence of radioactivity in the brain, either qualitatively or quantitatively, does not support the concept of Sevitt that cerebral fat embolism is the most important factor in this condition.