The Rh blood group in humans is determined by a gene on chromosome 1. Adominant allele Rh+ produces blood type, and a recessive allele generates Rh--. Elliptocytosis is an autosomal dominant disorder that produces abnormally shaped red blood cells that have a short life span resulting in hereditary anemia. A large family with elliptocytosis is tested for genetic linkage of Rh blood group and the disease. The lod score data are obtained for the family.