The Rh blood group system is highly complex both in the number of discrete antigens and in the existence of partial antigens, especially D and e. Recently, several partial c antigens have been reported. Here we report findings on an African American man with sickle cell disease whose RBCs typed C+c+ and whose plasma contained anti-c. Hemagglutination tests, DNA extraction, PCR-RFLP, reticulocyte RNA isolation, RT-PCR cDNA analyses, cloning, and sequencing were performed by standard procedures. RBCs from the patient typed C+c+ but his plasma contained alloanti-c. DNA analyses showed the presence of