The purpose of this project is to determine the pattern of inheritance of primary iron overload in African American families and to identify the genetic defect. The iron status of index subjects and family members will be determined by measuring transferrin saturation and serum ferritin, and the genetic pattern will be studied with segregation analysis. The chromosomal localization of the iron-loading locus will be pursued by determining HLA haplotypes, by testing for HFE gene mutations, by sequencing portions of genes for molecules involved in iron metabolism, by analyzing polymorphisms in these genes by PCR, by employing molecular methods to screen the genome, and by testing for linkage to iron phenotype with lod scores. Loci for proteins important in iron metabolism will be examined as candidate genes.