A technique is described for perfusing the parametrial fat pad of the rat. The rate of flow through the tissue was dependent on temperature, pressure, and the protein composition of the perfusing fluid. The latter also had a pronounced effect on the rate of edema formation in the tissue. The rate of fatty acid release by perfused adipose tissue was affected by the nutritional state of the fat donor and by the composition of the perfusing fluid. Tissue from fed rats did not release fatty acids. Adipose tissue from fasted rats released fatty acids when the tissue was perfused with diluted blood (1.10) or 4% albumin solution but not when perfused with 8% albumin. Perfused tissue released fatty acids at a much faster rate than did incubated tissue. Diluted blood and serum inhibited the release of fatty acids by incubated adipose tissue.