The virus of bluetongue (BT) was 1st isolated and identified in the US in 1952 from sheep in California. A disease in sheep in Texas (soremuzzle) was observed in 1947, reported in 1952 and similarities to BT were discussed. It is possible BT existed in Texas for several years prior to that time. There are 23 immunologic serotypes of BT, and 5 are known to occur in the US. These are types 10, 11, 13, 17 and 2, the latter having been recognized only in 1983 in cattle in Florida. In the US, BT was 1st recognized as a disease of sheep, but by the 1960s BT was known to occur in cattle with clinical manifestations which could be mistaken for vesicular stomatitis, infectious bovine rhinotracheitis and foot-and-mouth disease. Epizootic hemorrhagic disease (EHD) of deer, caused by orbiviruses related serologically to BT, was 1st recognized in New Jersey in 1956. Two serotypes of EHD virus have been identified in the US.