Screening of the complete genome sequence from the yeast Saccharomyces cerevisiae has enabled us to compile a complete list of the genes encoding cytoplasmic ribosomal proteins in this organism. Putative ribosomal protein genes were selected primarily on the basis of the sequence similarity of their products with ribosomal proteins from other eukaryotic organisms, in particular the rat. These genes were subsequently screened for typical yeast rp-gene characteristics, viz. (1) a high codon adaptation index; (2) their promoter structure and (3) their responses to changes in growth conditions. The yeast genome appears to carry 78 different genes, of which 59 are duplicated, encoding 32 different small-subunit and 46 large-subunit proteins. A new nomenclature for these ribosomal proteins is proposed.