Mammalian (rat) ribosomes have 80 proteins; the sequence of amino acids in 75 have been determined. What has been learned of the structure of the rat ribosomal proteins is reviewed with particular attention to their evolution and to amino acid sequence motifs. The latter include: clusters of basic or acidic residues; sequence repeats or shared sequences; zinc finger domains; bZIP elements; and nuclear localization signals. The occurrence and the possible significance of phosphorylated residues and of ubiquitin extensions is noted. The characteristics of the mRNAs that encode the proteins are summarized. The relationship of the rat ribosomal proteins to the proteins in ribosomes from humans, yeast, archaebacteria, and Escherichia coli is collated.