In 18 cats the omentum was mobilized, transposed, and placed directly upon the pia mater of the spinal cord. Within 2 months, vascular anastomoses developed at the omento-spinal cord interface and, as demonstrated by India ink perfusion, communicated widely with the cord's intramedullary vessels. Light and scanning electron microscopy (SEM) of the interface revealed the development of a "fibrous coat" of Goldsmith in continuity with the edges of the dura mater. It consisted mainly of a matrix of collagen fiber and fibroblasts, well vascularized with sinusoids, capillaries, arterioles and venules. The sinusoids, as identified by SEM, were present in both the fibrous coat and adjacent omentum, were lined with attenuated endothelium, and had multiple communications. The possible significance of the sinusoidal formation is discussed in this report.