The amino acid sequences of the rat 60S ribosomal subunit proteins L4 and L41 were deduced from the sequences of nucleotides in recombinant cDNAs. Ribosomal protein L4 has 421 amino acids; the molecular weight is 47,280. L41 is the smallest ribosomal protein; it has 25 amino acids and a molecular weight of 3,454. Hybridization of the cDNAs to digests of nuclear DNA suggests that there are 7 to 8 copies of the L4, and 9 to 12 of the L41, genes. The mRNA for L4 is about 1,500 nucleotides in length and that for L41 about 500 nucleotides. The 5' noncoding sequence of the L4 cDNA is exceptional in that it has, in addition to a short polypyrimidine sequence at the 5' end, a second stretch of 15 consecutive pyrimidines near the site of initiation of translation. The 3' noncoding sequence of the L41 mRNA is unusual in that it is at least 246 nucleotides long. Rat L4 and L41 are related to ribosomal proteins from other eukaryotes.