Cycling eukaryotic cells rapidly re-establish the nuclear envelope and internal architecture following mitosis. Studies with a specific anti-nucleosome antibody recently demonstrated that the surface ("epichromatin") of interphase and mitotic chromatin possesses a unique and conserved conformation, suggesting a role in postmitotic nuclear reformation. Here we present evidence showing that the anionic glycerophospholipid phosphatidylserine is specifically located in epichromatin throughout the cell cycle and is associated with nucleosome core histones. This suggests that chromatin bound phosphatidylserine may function as a nucleation site for the binding of ER and re-establishment of the nuclear envelope.