Structure and function of isolated liver ribosomes from 10 dogs subjected to 1 h of hepatic artery ligation (HAL) or hemorrhagic shock were studied. A shift of polyribosomes to monoribosomes and a decreased capacity to incorporate amino acids into proteins were seen in both experimental conditions. The effects were more pronounced in hemorrhagic shock. Both structural and functional changes were reversible after HAL. In the shock experiments a slight increase of the ribosomal activity was seen after reinfusion but the initial values were not reached during the 2 h after the shock period. Some of the underlying mechanisms of altered ribosomal structure and function in liver ischemia are discussed.