In previous studies, we have described, for each of the five human immunoglobulin IGHG (C gamma) genes, BamHI, SacI and BamHI/SacI allelic restriction fragments. Further, we have determined BS (BamHI/SacI) linkage groups of alleles for the whole of the IGHG loci and we have demonstrated correlation with the Gm alleles and haplotypes. In this paper we characterize more precisely the polymorphism of the IGHG genes and, consequently, the structure and evolution of this multigene family, using the restriction enzyme BstEII and two different probes, a IGHG (C gamma) probe and a G3 (C gamma 3) specific probe. Alleles and haplotypes of the BstEII restriction fragments have been defined with reference to the BS alleles and haplotypes. New RFLPs of the IGHG genes are described and unambiguous correlations have been established with most of the Gm alleles and haplotypes. Thus, the IGHG gene RFLPs strengthen the Gm polymorphisms as powerful tools for the characterization of populations, disease and genetic marker linkage analyses, forensic medicine and evolution of these IGHG genes.