The partial nucleotide sequence for an Fc-receptor gene from an M-type 76 group A streptococcus was determined. DNA sequence analysis revealed considerable sequence similarity between the Fc-receptor and M-protein genes in their proposed promoter regions, signal sequences, and 3' termini. Additional analysis indicated that the deduced Fc-receptor protein contains a proline-rich region and membrane anchor region highly similar to that of M protein. In view of these results, we postulated that Fc-receptor and M-protein genes of group A streptococci are the products of gene duplication from a common ancestral gene. It is proposed that DNA sequence similarity between these two genes may allow for extragenic homologous recombination as a means of generating antigenic diversity in these two surface proteins.