The yolk platelets found in oocytes from the toad Xenopuslaevis have been studied by electron microscopy and X-ray diffraction in the first stages of a low-resolution structure determination. The crystalline nature of the platelet has been confirmed, and powder photographs of four forms of the lipoprotein-phosvitin complex have been indexed. The X-ray results from wet native crystals are most consistent with an orthorhombic lattice of unit cell dimensions a = 88·5 Å, b = 174·8 Å, and c = 198·9 Å. Nine different views of the lattice have been found in electron micrographs of fragments broken from the microcrystals and negatively stained with uranyl acetate. Optical diffraction patterns from these micrographs have been indexed in terms of the lattice derived from the X-ray diffraction results.