Testes from guinea-pig and chinchilla were studied with the electron microscope after vascular perfusion of glutaraldehyde or acrolein. The improved preservation achieved by this method of fixation permitted the demonstration of an extensive system of very thin-walled lymphatic sinusoids in the interstitial tissue. The lymphatic endothelium is closely applied to the lamina propria of the seminiferous tubules on the one side and to the clusters of interstitial cells on the other. It is suggested that these lymphatics may have an important function in the distribution of androgens within the testis, in addition to their role in returning to the general circulation the large amount of serum protein that escapes from the highly permeable blood capillaries of the interstitium.