To investigate the genetic basis of the Rh polypeptide gene, we attempted the isolation of cDNA clones for Rh polypeptide from a family with the RhD-positive and RhD-negative phenotypes using the reverse transcription (RT)-PCR method for each reticulocyte RNAs followed by subcloning. The isolated cDNAs showed the existence of another Rh-related clone (RhPII-1 cDNA, tentative designation) besides the RhPI and RhPII cDNA clones reported previously by us. The RhPII-1 cDNA had a single nucleotide substitution with one amino acid substitution compared with the RhPII cDNA:substitution C-->T in nucleotide 380, changing codon 127 from GCG to GTG (Ala-->Val). The RhPI, RhPII, and RhPII-1 cDNA clones were detected in all individuals by the PCR experiment. This suggests that the Rh polypeptide genes have been inherited from parents and might be highly polymorphic. The PCR amplification of an RhPII-specific region from reticulocyte RNA and genomic DNA in all the family proved that the RhPII gene exists in both RhD-positive and RhD-negative individuals. By Southern-blot analysis of the DNAs from the family, two independent polymorphisms concerning the RhC/c and RhD/d phenotypes were observed. These results demonstrate that the RhPI and RhPII genes are also present in the RhD-negative donors, and the RhPII-related cDNAs encode not the RhD, but the RhC/c and/or E/e, polypeptides.