This report is a preliminary description of the cloning, DNA sequence determination, and expression of the protein A gene from Staphylococcus aureus in Escherichia coli and yeast recombinant host systems. The deduced amino acid sequences of the Fc-binding domains agree well with a previously published peptide analysis. The deduced amino acid sequence of the cell wall anchorage domain reveals 11 short repeating units (designated S repeats). The S repeat consensus sequence is the octapeptide Lys-Pro-Gly-Lys-glu-Asp-Gly-Asn. The potential for the use of genetic engineering to enhance the therapeutic utility of the protein A molecule is also discussed.