The study is a population based analysis of genetic variation of blood group antigens in three defined, ancient and still conserved Ethiopian sub-populations. Blood samples will be collected in distinct remote areas of Ethiopia and be analyzed at DTM/CC/NIH using standard serologic methods and modern molecular genotyping systems. Samples of red blood cells, plasma, DNA and cDNA will also be stored for future additional study, like high throughput sequencing. The study will allow a systematic analysis of the distribution of blood group antigens in three Ethiopian sub-populations. The populations are known to differ in malaria and sickle cell disease prevalence and environmental factors like other tropical infectious diseases and oxygen pressure. The ethnic group living in the Ethiopian highland is possibly exposed to low oxygen pressure for the longest period of any human population. We expect to describe differences associated with environmental influences (high altitude, low land tropical, and low land desert). We also expect to detect new alleles that may allow novel insight into the correlation of genotypes and phenotypes. The study was examined by the IRB of NHLBI and approved through PCSC on 1/11/2011 as NIH protocol 11-CC-N086.