Preliminary studies on the morphology of the oocysts of several species of Eimeria of cattle, using electron microscopy have shown the surface structure of the oocysts of several species. The entire surface of E. bovis was covered with ridges and giving an overall rough appearance to the oocyst. The surface of E. canadensis appeared cloudy relatively smooth with small scattering papillae and the border of the wall appeared smooth. The oocyst of E. alabamensis contained large micropores of different sizes in its wall~ At least 9 clear pores were found on the surface of oocyst. The surface of E. ellipsoidalis appeared"smooth with no distinguishing features. While E. brasiliensis entire surface was covered with small, very fine papillae. The polar cap appears to be thicker at the top and thinner at its point of attachment to the wall. The oocyst of species of E. auburnensis appeared cloudy and the wall is covered with very tiny papillae. The papillae look to be embedded in the matrix of the wall. However, scattered papillae were also seen on the oocyst wall of E. cylindrica.