1. Wound fluid was collected from a subcutaneous lesion in the shoulder region of sheep by implanting a PTFE sampling chamber from which a catheter led to the skin surface. 2. The neutrophil granulocyte numbers and prostaglandin content of the wound fluid were studied, prostaglandins being identified by thin layer chromatography and measured by bio-assay. The major prostaglandin component was E2. 3. There was no clear relation between the amounts of prostaglandin present and the numbers of neutrophils in the fluid. 4. A subcutaneously implanted double chamber permitted perfusion of the lesion and thereby the study of the rate of prostaglandin production and the rate of disappearance of isotopically labelled prostaglandin from the lesion. The rate of leucocyte entry into the wound fluid could also be measured. 5. When the cutaneous muscle through which the chamber had been implanted was biopsied and incubated in vitro it was found to produce prostaglandin E2 in quantities which could be correlated with the weight of the incubated muscle. 6. These results suggest that a major contributor to the prostaglandin content of the wound fluid is the cutaneous striped muscle.