We have isolated cDNA clones encoding the human homologue (hL30) of yeast ribosomal protein (r-protein) L30. The hL30 nucleotide (nt) sequence shows high homology to the yeast sequences and also to a partial Xenopus laevis sequence previously identified as an immunoglobulin heavy chain. The 5' end of hL30 is pyrimidine-rich, as is the case for most other mammalian r-protein mRNAs. The open reading frame consists of 157 codons with a C-terminal region that is different from corresponding regions of the yeast proteins. In several human tissue culture cells, the mRNA encoding hL30 is approx. 700 nt in length.