Egg yolk lipoproteins were separated into four major density classes by conventional ultracentrifugation, and each class was resolved further by thin-layer chromatography on hydroxylapatite. The plates were developed in special saturation chambers with phosphate buffers of 0.4, 0.6, 1.2, and 2.0 M for 2 h, and bands were located by exposure to iodine vapor or by spraying with ninhydrin. The low density fraction and the low density fraction of the granule each gave two subfractions, while the phosvitin–lipovitellin fraction yielded three components and the water-soluble fraction four components. The additional resolution apparently was due to differences in lipid and protein composition and structure, as well as to the content of protein-bound phosphorus. The described separations offer special advantages for the study of the lipid parts of the lipoprotein complexes.