We present here the cloning and the entire sequence of one of the two gene copies coding for ribosomal protein (r-protein) S8 in Xenopus laevis (corresponding to r-protein S7 in rat) and its flanking regions. The S8a gene contains seven exons and six introns for a total length of about 12,700 bp coding for a mRNA of 663 nucleotides (nt) plus a poly(A) tail. Mapping of the 5' end of the gene has shown that the transcription start point is located in a pyrimidine-rich tract, as has been observed for all r-protein-encoding genes of X. laevis and other vertebrates so far characterized. A computer analysis of the S8a sequence has revealed the presence of a 220-nt sequence repeated, with some variations, once in each of the six introns. RNA analysis by hybridization with oligo probes specific for the two gene copies coding for r-protein S8 has demonstrated that the two of them are expressed at similar levels both in oocytes and in embryos.