Abstract: This study deals with soluble proteins obtained by saline extraction from rat liver nuclei isolated in sucrose media. Included are descriptions of exploratory experiments, the method of isolation adopted, and the electrophoretic behaviour of the soluble proteins obtained from normal animals, from starved animals during recovery and from animals given a liver carcinogen in their diet. In mobility these proteins correspond to the more basic of the soluble cytoplasmic proteins, but do not include histones, and they are retained in the nucleus by ion binding. Apparently each class of proteins binds at specific sites, each binding process has individual characteristics, and the presence of divalent metal ions is important in some cases. In resting animals, and in starved animals in which liver metabolism is below normal, these nuclear proteins yield electrophoretic patterns that give little indication of individual components. During recovery or adaptation, when new structural proteins and enzymes are being produced, individual components are clearly evident in the patterns, with obvious increases in certain components. It is clear that changes in the physiological status of the liver are accompanied by changes in the nature of the soluble proteins that are retained in the liver cell nuclei by ion binding. Apparently these soluble nuclear proteins are involved in liver cell metabolism.