This is a case study of a 24-year-old male, having total knee arthroplasty, who is found to have an anti-f antibody, and denies history of previous blood product injection or blood transfusion. The anti-f antibody is produced due to exposure to the f antigen, and is one of the Rh blood group system's compound antigens expressed when the c and e alleles are in the cis position on the Rh chromosome. Patients with anti-f requiring transfusion could safely be transfused with units of blood lacking both the c and e antigens and units lacking only the c antigen.